diff --git a/README.md b/README.md
index 2200c0f..89a72d4 100644
--- a/README.md
+++ b/README.md
@@ -1,112 +1,121 @@
-# **FEZrs**     
-
-[![DOI](https://zenodo.org/badge/710286874.svg)](https://doi.org/10.5281/zenodo.14938038) [![Tests](https://github.com/FEZtool-team/FEZrs/actions/workflows/FEZrs_Tests.yml/badge.svg?branch=main)](https://github.com/FEZtool-team/FEZrs/actions/workflows/FEZrs_Tests.yml) [![Documentation](https://img.shields.io/website?url=https%3A%2F%2Ffeztool-team.github.io%2FFEZdocs%2Flibraries%2Ffezrs%2F&label=docs)](https://feztool-team.github.io/FEZdocs/libraries/fezrs/) [![Downloads/month](https://static.pepy.tech/badge/fezrs/month)](https://pepy.tech/project/fezrs) [![PyPI version](https://img.shields.io/pypi/v/fezrs.svg)](https://pypi.org/project/fezrs/)
-[![Conda Version](https://img.shields.io/conda/vn/FEZtool/fezrs?label=Anaconda&color=orange&logo=anaconda)](https://anaconda.org/FEZtool/fezrs) ![License](https://img.shields.io/pypi/l/FEZrs) [![PyPI Downloads](https://static.pepy.tech/badge/fezrs)](https://pepy.tech/projects/fezrs) ![GitHub last commit](https://img.shields.io/github/last-commit/FEZtool-team/fezrs) [![Platform](https://img.shields.io/conda/pn/feztool/fezrs?color=blue&label=Platform&style=flat)](https://anaconda.org/feztool/fezrs) ![GitHub stars](https://img.shields.io/github/stars/FEZtool-team/FEZrs?style=social)
-
-**FEZrs** is an advanced Python library developed by [**FEZtool**](https://feztool.com/) for Remote Sensing applications. It provides a set of powerful tools for image processing, feature extraction, and analysis of geospatial data.
-
-## **Features**
-
-✅ Apply various image filtering techniques (Gaussian, Laplacian, Sobel, Median, Mean)  
-✅ Contrast enhancement and edge detection  
-✅ Support for geospatial raster data (TIFF)  
-✅ Designed for remote sensing and satellite imagery analysis  
-✅ Easy integration with FastAPI for web-based processing
-
-## Documentation
-
-Full documentation, API references, tutorials, and examples are available here:
-https://feztool-team.github.io/FEZdocs/libraries/fezrs/
-
-## **📦 Installation**
-
-You can install **FEZrs** using your preferred Python package manager:
-
-### Using `pip` (PyPI)
-
-```bash
-pip install fezrs
-```
-
-### Using `conda` (Anaconda)
-
-```bash
-conda install -c FEZtool fezrs
-```
-
-### Using `mamba` (optional, faster conda alternative)
-
-```bash
-mamba install FEZtool::fezrs
-```
-
-> **Note:** The `mamba` command requires [Mamba](https://github.com/mamba-org/mamba) to be installed. If it's not installed, use the `conda` command instead.
-
-## **Usage**
-
-Example of applying a Gaussian filter to an image:
-
-```python
-from fezrs import EqualizeRGBCalculator
-
-equalize = EqualizeRGBCalculator(
-    blue_path="path/to/your/image_band.tif",
-    green_path="path/to/your/image_band.tif",
-    red_path="path/to/your/image_band.tif",
-)
-
-equalize.chart_export(output_path="./your/export/path")
-equalize.execute(output_path="./your/export/path")
-```
-
-## **Modules**
-
-- `KMeansCalculator`
-- `GaussianCalculator`
-- `LaplacianCalculator`
-- `MeanCalculator`
-- `MedianCalculator`
-- `SobelCalculator`
-- `GLCMCalculator`
-- `HSVCalculator`
-- `IRHSVCalculator`
-- `AdaptiveCalculator`
-- `AdaptiveRGBCalculator`
-- `EqualizeCalculator`
-- `EqualizeRGBCalculator`
-- `FloatCalculator`
-- `GammaCalculator`
-- `GammaRGBCalculator`
-- `LogAdjustCalculator`
-- `OriginalCalculator`
-- `OriginalRGBCalculator`
-- `SigmoidAdjustCalculator`
-- `PCACalculator`
-- `AFRICalculator`
-- `BICalculator`
-- `NDVICalculator`
-- `NDWICalculator`
-- `SAVICalculator`
-- `UICalculator`
-- `SpectralProfileCalculator`
-
-## **Contributing**
- 
-We welcome contributions! To contribute:
-
-1. Fork the repository
-2. Create a new branch (`git checkout -b feature-name`)
-3. Commit your changes (`git commit -m "Add new feature"`)
-4. Push to your branch (`git push origin feature-name`)
-5. Open a Pull Request
-
-## **Acknowledgment**
-
-Special thanks to [**Chakad Cafe**](https://www.chakadcoffee.com/) for the coffee that kept us fueled during development! ☕
-
-## **License**
-
-This project is licensed under the [**Apache-2.0 license**.](https://github.com/FEZtool-team/FEZrs/edit/main/LICENSE)
-
-
-
+# **FEZrs**     
+
+[![DOI](https://zenodo.org/badge/710286874.svg)](https://doi.org/10.5281/zenodo.14938038) [![Tests](https://github.com/FEZtool-team/FEZrs/actions/workflows/FEZrs_Tests.yml/badge.svg?branch=main)](https://github.com/FEZtool-team/FEZrs/actions/workflows/FEZrs_Tests.yml) [![Documentation](https://img.shields.io/website?url=https%3A%2F%2Ffeztool-team.github.io%2FFEZdocs%2Flibraries%2Ffezrs%2F&label=docs)](https://feztool-team.github.io/FEZdocs/libraries/fezrs/) [![Downloads/month](https://static.pepy.tech/badge/fezrs/month)](https://pepy.tech/project/fezrs) [![PyPI version](https://img.shields.io/pypi/v/fezrs.svg)](https://pypi.org/project/fezrs/)
+[![Conda Version](https://img.shields.io/conda/vn/FEZtool/fezrs?label=Anaconda&color=orange&logo=anaconda)](https://anaconda.org/FEZtool/fezrs) ![License](https://img.shields.io/pypi/l/FEZrs) [![PyPI Downloads](https://static.pepy.tech/badge/fezrs)](https://pepy.tech/projects/fezrs) ![GitHub last commit](https://img.shields.io/github/last-commit/FEZtool-team/fezrs) [![Platform](https://img.shields.io/conda/pn/feztool/fezrs?color=blue&label=Platform&style=flat)](https://anaconda.org/feztool/fezrs) ![GitHub stars](https://img.shields.io/github/stars/FEZtool-team/FEZrs?style=social)
+
+**FEZrs** is an advanced Python library developed by [**FEZtool**](https://github.com/FEZtool-team) for Remote Sensing applications. It provides a set of powerful tools for image processing, feature extraction, and analysis of geospatial data.
+
+## **Features**
+
+✅ Apply various image filtering techniques (Gaussian, Laplacian, Sobel, Median, Mean)  
+✅ Contrast enhancement and edge detection  
+✅ Support for geospatial raster data (TIFF)  
+✅ Designed for remote sensing and satellite imagery analysis  
+✅ Easy integration with FastAPI for web-based processing
+
+## Documentation
+
+Full documentation, API references, tutorials, and examples are available here:
+https://feztool-team.github.io/FEZdocs/libraries/fezrs/
+
+## **📦 Installation**
+
+You can install **FEZrs** using your preferred Python package manager:
+
+### Using `pip` (PyPI)
+
+```bash
+pip install fezrs
+```
+
+### Using `conda` (Anaconda)
+
+```bash
+conda install -c FEZtool fezrs
+```
+
+### Using `mamba` (optional, faster conda alternative)
+
+```bash
+mamba install FEZtool::fezrs
+```
+
+> **Note:** The `mamba` command requires [Mamba](https://github.com/mamba-org/mamba) to be installed. If it's not installed, use the `conda` command instead.
+
+## **Usage**
+
+Example of applying a Gaussian filter to an image:
+
+```python
+from fezrs import EqualizeRGBCalculator
+
+equalize = EqualizeRGBCalculator(
+    blue_path="path/to/your/image_band.tif",
+    green_path="path/to/your/image_band.tif",
+    red_path="path/to/your/image_band.tif",
+)
+
+equalize.execute(output_path="./your/export/path")
+equalize.histogram_export(output_path="./your/export/path")
+```
+
+## **Modules**
+
+- `KMeansCalculator`
+- `GaussianCalculator`
+- `LaplacianCalculator`
+- `MeanCalculator`
+- `MedianCalculator`
+- `SobelCalculator`
+- `GLCMCalculator`
+- `HSVCalculator`
+- `IRHSVCalculator`
+- `AdaptiveCalculator`
+- `AdaptiveRGBCalculator`
+- `EqualizeCalculator`
+- `EqualizeRGBCalculator`
+- `FloatCalculator`
+- `GammaCalculator`
+- `GammaRGBCalculator`
+- `LogAdjustCalculator`
+- `OriginalCalculator`
+- `OriginalRGBCalculator`
+- `SigmoidAdjustCalculator`
+- `PCACalculator`
+- `AFRICalculator`
+- `BICalculator`
+- `NDVICalculator`
+- `NDWICalculator`
+- `SAVICalculator`
+- `UICalculator`
+- `SpectralProfileCalculator`
+- `MosaicCalculator`
+- `SVMCalculator`
+- `Landsat8Calculator`
+- `GeoeyeCalculator`
+- `BurnCalculator`
+- `IndicesCalculator`
+- `MagDirCalculator`
+- `SubDivCalculator`
+- `TimeCalculator`
+
+## **Contributing**
+ 
+We welcome contributions! To contribute:
+
+1. Fork the repository
+2. Create a new branch (`git checkout -b feature-name`)
+3. Commit your changes (`git commit -m "Add new feature"`)
+4. Push to your branch (`git push origin feature-name`)
+5. Open a Pull Request
+
+## **Acknowledgment**
+
+Special thanks to [**Chakad Cafe**](https://www.chakadcoffee.com/) for the coffee that kept us fueled during development! ☕
+
+## **License**
+
+This project is licensed under the [**Apache-2.0 license**.](https://github.com/FEZtool-team/FEZrs/edit/main/LICENSE)
+
+
+
diff --git a/docs/filters.md b/docs/filters.md
index d7a1044..6fca6d9 100644
--- a/docs/filters.md
+++ b/docs/filters.md
@@ -15,7 +15,7 @@ The `filters` module provides a comprehensive suite of digital image processing
             ▼                                   ▼
 [Linear Shift-Invariant Filters]     [Non-Linear Statistical Filters]
 ├─ MeanCalculator                    └─ MedianCalculator
-├─ GuassianCalculator
+├─ GaussianCalculator
 ├─ SobelCalculator
 └─ LaplacianCalculator
 ```
@@ -54,11 +54,11 @@ This approach minimizes edge artifacts and prevents artificial gradient boundari
 
 ## Comprehensive Class Specifications
 
-### GuassianCalculator` — Isotropic Low-Pass Smoothing
+### GaussianCalculator` — Isotropic Low-Pass Smoothing
 
 #### Scientific & Physical Objective
 
-The algorithmic goal of `GuassianCalculator` is to apply an isotropic low-pass filter to remove continuous high-frequency background noise (such as thermal electronic sensor noise or atmospheric scattering). This smoothing step helps maintain structural boundaries and edge locations more effectively than a standard unweighted box-average filter.
+The algorithmic goal of `GaussianCalculator` is to apply an isotropic low-pass filter to remove continuous high-frequency background noise (such as thermal electronic sensor noise or atmospheric scattering). This smoothing step helps maintain structural boundaries and edge locations more effectively than a standard unweighted box-average filter.
 
 #### Theoretical Foundation & Mathematical Formulations
 
@@ -102,10 +102,10 @@ In the frequency domain, the Fourier transform of a Gaussian kernel is itself a
 
 ```Python
 from pathlib import Path
-from fezrs.tools.filters import GuassianCalculator
+from fezrs.tools.filters import GaussianCalculator
 
 # Initialize low-pass isotropic Gaussian engine
-gaussian_blur = GuassianCalculator(
+gaussian_blur = GaussianCalculator(
     tif_path=Path("./data/Landsat8_Band5.tif")
 )
 
diff --git a/docs/image-enhancement.md b/docs/image-enhancement.md
index bd0105d..1d719b0 100644
--- a/docs/image-enhancement.md
+++ b/docs/image-enhancement.md
@@ -10,7 +10,7 @@ The `enhancement` module delivers a comprehensive suite of linear and non-linear
                                           │
                                           ▼
                       ┌───────────────────────────────────────┐
-                      │    fezrs.tools.enhancement Module     │
+                      │    fezrs.tools.image_enhancement Module     │
                       └───────────────────┬───────────────────┘
                                           │
          ┌────────────────────────────────┴────────────────────────────────┐
@@ -96,7 +96,7 @@ $$I_{\text{eq}}(x, y) = \frac{1}{N} \sum_{j=1}^{\text{rank}(I(x, y))} \text{coun
 
 ```Python
 from pathlib import Path
-from fezrs.tools.enhancement import EqualizeCalculator
+from fezrs.tools.image_enhancement import EqualizeCalculator
 
 # Initialize global histogram equalization pipeline
 equalizer = EqualizeCalculator(nir_path=Path("./data/Hazy_NIR.tif"))
@@ -145,7 +145,7 @@ $$I_{\text{CLAHE}}(x, y) = \text{BilinearInterpolate}\left(T_{t_1}, T_{t_2}, T_{
 
 ```Python
 from pathlib import Path
-from fezrs.tools.enhancement import AdaptiveCalculator
+from fezrs.tools.image_enhancement import AdaptiveCalculator
 
 # Execute local adaptive contrast optimization via CLAHE
 clahe_engine = AdaptiveCalculator(
@@ -195,7 +195,7 @@ Where:
 
 ```Python
 from pathlib import Path
-from fezrs.tools.enhancement import GammaCalculator
+from fezrs.tools.image_enhancement import GammaCalculator
 
 # Initialize power-law gamma transformation engine
 gamma_corrector = GammaCalculator(
diff --git a/docs/pca.md b/docs/pca.md
index ccd3c4a..56fbbd1 100644
--- a/docs/pca.md
+++ b/docs/pca.md
@@ -127,7 +127,25 @@ These higher-order components capture progressively smaller variations in the da
         
     - `swir2_path` (`str` | `Path`): File path to the Short-Wave Infrared 2 band raster layer.
         
-    - `selectBand` (`Literal["red","green","blue","nir","swir1","swir2", None]`): Optional parameter. Selects a specific input band to map against the component outputs during specialized diagnostic profiling.
+    - `component` (`int | None`): Principal component to inspect, numbered $1 \dots 6$ in order of decreasing explained variance. Required by `histogram_export()`.
+
+    - `standardize` (`bool`, default `False`): Decompose the **correlation** matrix instead of the covariance matrix, by scaling each band to unit variance first. `sklearn` decomposes the covariance matrix, which lets whichever band carries the widest digital-number range dominate the leading components regardless of how much information it holds. Standardized PCA is the usual choice for multispectral work where band ranges differ substantially.
+
+    - `selectBand` (`Literal["red","green","blue","nir","swir1","swir2", None]`): **Deprecated.** A band name that resolves to a fixed component index, emitting a `DeprecationWarning` naming the component it maps to.
+
+    > **Why `selectBand` was replaced.** A principal component is a linear combination of *all six* input bands, weighted by the corresponding eigenvector, so **no component corresponds to an input band**. The parameter indexed into a fixed name-to-index map, meaning `selectBand="red"` plotted the **first principal component** and titled the figure "Histogram of PCA Band Red" — attributing the output to a band that did not produce it. A user selecting `"swir2"` to inspect the SWIR2 response was shown the fifth component. The mapping order was also arbitrary: it followed the insertion order of the band dictionary in `FileHandler.__init__`, which is why it read `red, nir, blue, swir1, swir2, green` rather than any order a user would expect.
+
+#### Eigen-structure Accessors
+
+Both raise `RuntimeError` before `process()` has run.
+
+- `explained_variance_ratio_` (`np.ndarray`, shape `(6,)`): Share of total variance per component, ordered decreasing. On the bundled Landsat subset PC1 carries 90.6%, PC2 7.3% and PC3 1.8% — the strong concentration typical of multispectral imagery, where PC1 largely captures scene brightness.
+
+- `components_` (`np.ndarray`, shape `(6, 6)` as `(component, band)`): Eigenvector loadings, with band order given by `band_order`.
+
+    **Loadings, not variance share, are what identify a useful component.** A target is isolated by the component in which the diagnostic bands carry high loadings of *opposing* sign, and that component is frequently not the one with the most variance — PC1 usually just encodes albedo.
+
+> **Component signs are fixed.** Eigenvector signs are mathematically arbitrary, so without a convention the same scene can yield an inverted component image between runs, or between a scene and a crop of it. FEZrs forces the largest-magnitude loading of each component positive, making repeated runs directly comparable.
 
 #### Processing Pipeline Lifecycle (`process()`)
 
diff --git a/docs/spectral-indices.md b/docs/spectral-indices.md
index dbae6e6..c6bf71a 100644
--- a/docs/spectral-indices.md
+++ b/docs/spectral-indices.md
@@ -232,7 +232,7 @@ The following matrix cross-references the required sensor channels, target range
 
 ```Python
 from pathlib import Path
-from fezrs.tools.indices import NDVICalculator
+from fezrs.tools.spectral_indices import NDVICalculator
 
 # Instantiate the NDVI processing engine using Landsat 8 paths
 ndvi_engine = NDVICalculator(
@@ -253,7 +253,7 @@ ndvi_engine.execute(
 
 ```Python
 from pathlib import Path
-from fezrs.tools.indices import NDWICalculator
+from fezrs.tools.spectral_indices import NDWICalculator
 
 # Instantiate McFeeters NDWI calculator using Sentinel-2 paths
 ndwi_engine = NDWICalculator(
diff --git a/example/clustering.py b/example/clustering.py
index c77e3be..087ea4a 100644
--- a/example/clustering.py
+++ b/example/clustering.py
@@ -1,5 +1,18 @@
+"""
+K-means clustering example.
+
+Paths resolve relative to this file, so the script runs from any directory.
+"""
+
+from pathlib import Path
+
 from fezrs import KMeansCalculator
 
-KMeansCalculator(nir_path="./data/nir.tif", n_clusters=4, random_state=0).execute(
-    output_path="./outputs/clustering",
+DATA = Path(__file__).parent / "data"
+OUTPUTS = Path(__file__).parent / "outputs"
+
+KMeansCalculator(
+    nir_path=DATA / "nir.tif", n_clusters=4, random_state=0
+).execute(
+    output_path=OUTPUTS / "clustering",
 )
diff --git a/example/filters.py b/example/filters.py
index 5d43132..701edc4 100644
--- a/example/filters.py
+++ b/example/filters.py
@@ -1,3 +1,11 @@
+"""
+Spatial filtering examples.
+
+Paths resolve relative to this file, so the script runs from any directory.
+"""
+
+from pathlib import Path
+
 from fezrs import (
     GaussianCalculator,
     LaplacianCalculator,
@@ -6,24 +14,18 @@
     SobelCalculator,
 )
 
-GaussianCalculator(
-    tif_path="./data/pan_img.tif",
-).execute(
-    output_path="./outputs/filter",
-)
+DATA = Path(__file__).parent / "data"
+OUTPUTS = Path(__file__).parent / "outputs"
 
-LaplacianCalculator(tif_path="./data/pan_img.tif", kernel_size=7).execute(
-    output_path="./outputs/filter",
-)
+PAN = DATA / "pan_img.tif"
+FILTER_OUTPUT = OUTPUTS / "filter"
 
-MeanCalculator(tif_path="./data/pan_img.tif").execute(
-    output_path="./outputs/filter",
-)
+GaussianCalculator(tif_path=PAN).execute(output_path=FILTER_OUTPUT)
 
-MedianCalculator(tif_path="./data/pan_img.tif", kernel_size=5).execute(
-    output_path="./outputs/filter",
-)
+LaplacianCalculator(tif_path=PAN, kernel_size=7).execute(output_path=FILTER_OUTPUT)
 
-SobelCalculator(tif_path="./data/pan_img.tif", kernel_size=7).execute(
-    output_path="./outputs/filter",
-)
+MeanCalculator(tif_path=PAN).execute(output_path=FILTER_OUTPUT)
+
+MedianCalculator(tif_path=PAN, kernel_size=5).execute(output_path=FILTER_OUTPUT)
+
+SobelCalculator(tif_path=PAN, kernel_size=7).execute(output_path=FILTER_OUTPUT)
diff --git a/example/hsv.py b/example/hsv.py
index 40cbc90..03d953f 100644
--- a/example/hsv.py
+++ b/example/hsv.py
@@ -1,12 +1,23 @@
+"""
+HSV colour-space example.
+
+Paths resolve relative to this file, so the script runs from any directory.
+"""
+
+from pathlib import Path
+
 from fezrs import HSVCalculator
 
+DATA = Path(__file__).parent / "data"
+OUTPUTS = Path(__file__).parent / "outputs"
+
 HSVCalculator(
-    blue_path="./data/blue.tif",
-    green_path="./data/green.tif",
-    nir_path="./data/nir.tif",
+    blue_path=DATA / "blue.tif",
+    green_path=DATA / "green.tif",
+    nir_path=DATA / "nir.tif",
     channel="hsv",
 ).execute(
-    output_path="./outputs/hsv",
+    output_path=OUTPUTS / "hsv",
     show_axis=False,
     show_colorbar=False,
 )
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diff --git a/example/pca.py b/example/pca.py
index 9e7e19a..f2987c4 100644
--- a/example/pca.py
+++ b/example/pca.py
@@ -1,14 +1,30 @@
+"""
+Principal component analysis example.
+
+Paths resolve relative to this file, so the script runs from any directory.
+"""
+
 from pathlib import Path
+
 from fezrs import PCACalculator
 
-PCACalculator(
-    blue_path= Path.cwd() / "./example/data/blue.tif",
-    green_path= Path.cwd() / "./example/data/green.tif",
-    red_path= Path.cwd() / "./example/data/red.tif",
-    nir_path= Path.cwd() / "./example/data/nir.tif",
-    swir1_path= Path.cwd() / "./example/data/swir_1.tif",
-    swir2_path= Path.cwd() / "./example/data/swir_2.tif",
-    selectBand="blue",
-).execute(
-    output_path=Path.cwd() /"./example/outputs/pca",
-).histogram_export(output_path=Path.cwd() /"./example/outputs/pca")
+DATA = Path(__file__).parent / "data"
+OUTPUTS = Path(__file__).parent / "outputs"
+
+calculator = PCACalculator(
+    blue_path=DATA / "blue.tif",
+    green_path=DATA / "green.tif",
+    red_path=DATA / "red.tif",
+    nir_path=DATA / "nir.tif",
+    swir1_path=DATA / "swir_1.tif",
+    swir2_path=DATA / "swir_2.tif",
+    component=1,
+)
+
+calculator.execute(output_path=OUTPUTS / "pca")
+calculator.histogram_export(output_path=OUTPUTS / "pca")
+
+# Variance share and band loadings are what decide which component is worth
+# inspecting -- the largest component is not always the informative one.
+for index, share in enumerate(calculator.explained_variance_ratio_, start=1):
+    print(f"PC{index}: {share:.1%} of total variance")
diff --git a/fezrs/__init__.py b/fezrs/__init__.py
index 00e5cc4..f830c5e 100644
--- a/fezrs/__init__.py
+++ b/fezrs/__init__.py
@@ -44,8 +44,14 @@
     MosaicCalculator,
 )
 
-from fezrs.tools.import_tools.geoeye_calculator import Geoeye_Calculator
-from fezrs.tools.import_tools.landsat8_calculator import Landsat8_Calculator
+from fezrs.tools.import_tools.geoeye_calculator import (
+    Geoeye_Calculator,
+    GeoeyeCalculator,
+)
+from fezrs.tools.import_tools.landsat8_calculator import (
+    Landsat8_Calculator,
+    Landsat8Calculator,
+)
 
 from fezrs.tools.change_detection.burn_calculator import BurnCalculator
 from fezrs.tools.change_detection.indices_calculator import IndicesCalculator
@@ -87,7 +93,9 @@
     "SpectralProfileCalculator",
     "MosaicCalculator",
     "Geoeye_Calculator",
+    "GeoeyeCalculator",
     "Landsat8_Calculator",
+    "Landsat8Calculator",
     "BurnCalculator",
     "IndicesCalculator",
     "MagDirCalculator",
diff --git a/fezrs/base.py b/fezrs/base.py
index 73eb7db..b8e55b6 100644
--- a/fezrs/base.py
+++ b/fezrs/base.py
@@ -74,7 +74,7 @@ def _export_file(
         show_axis: bool = False,
         colormap: str = None,
         show_colorbar: bool = False,
-        filename_prefix: str = "Tool_output",
+        filename_prefix: str | None = None,
         dpi: int = 500,
         bbox_inches: str = "tight",
         grid: bool = True,
@@ -101,7 +101,11 @@ def _export_file(
         Returns:
             The path to the saved image file.
         """
-        filename_prefix = self.__tool_name
+        # Fall back to the tool name only when the caller did not choose a
+        # prefix. Previously the argument was accepted, documented, and then
+        # overwritten on this line before it was ever used.
+        if filename_prefix is None:
+            filename_prefix = self.__tool_name
 
         # Check output property is not empty
         if self._output is None:
@@ -144,7 +148,7 @@ def execute(
         show_axis: bool = False,
         colormap: str = None,
         show_colorbar: bool = False,
-        filename_prefix: str = "Tool_output",
+        filename_prefix: str | None = None,
         dpi: int = 500,
         bbox_inches: str = "tight",
         grid: bool = True,
@@ -184,5 +188,9 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            # Forwarded rather than dropped: these were declared and documented
+            # on execute() but never reached plt.subplots().
+            1 if nrows is None else nrows,
+            1 if ncols is None else ncols,
         )
         return self
diff --git a/fezrs/media/__init__.py b/fezrs/media/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/fezrs/tools/change_detection/__init__.py b/fezrs/tools/change_detection/__init__.py
new file mode 100644
index 0000000..2627e68
--- /dev/null
+++ b/fezrs/tools/change_detection/__init__.py
@@ -0,0 +1,5 @@
+from .burn_calculator import BurnCalculator
+from .indices_calculator import IndicesCalculator
+from .magdir_calculator import MagDirCalculator
+from .subdiv_calculator import SubDivCalculator
+from .time_calculator import TimeCalculator
diff --git a/fezrs/tools/change_detection/burn_calculator.py b/fezrs/tools/change_detection/burn_calculator.py
index 0216ebf..7c19fca 100644
--- a/fezrs/tools/change_detection/burn_calculator.py
+++ b/fezrs/tools/change_detection/burn_calculator.py
@@ -50,7 +50,7 @@ def execute(
         show_axis=True,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/change_detection/indices_calculator.py b/fezrs/tools/change_detection/indices_calculator.py
index 22c3fd0..e34c71e 100644
--- a/fezrs/tools/change_detection/indices_calculator.py
+++ b/fezrs/tools/change_detection/indices_calculator.py
@@ -71,7 +71,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/change_detection/magdir_calculator.py b/fezrs/tools/change_detection/magdir_calculator.py
index ebeda1b..ac45155 100644
--- a/fezrs/tools/change_detection/magdir_calculator.py
+++ b/fezrs/tools/change_detection/magdir_calculator.py
@@ -118,7 +118,7 @@ def execute(
         show_axis=True,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/change_detection/subdiv_calculator.py b/fezrs/tools/change_detection/subdiv_calculator.py
index ea4f1a0..990dbf5 100644
--- a/fezrs/tools/change_detection/subdiv_calculator.py
+++ b/fezrs/tools/change_detection/subdiv_calculator.py
@@ -57,7 +57,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/change_detection/time_calculator.py b/fezrs/tools/change_detection/time_calculator.py
index 341b5f3..8af55c2 100644
--- a/fezrs/tools/change_detection/time_calculator.py
+++ b/fezrs/tools/change_detection/time_calculator.py
@@ -47,7 +47,7 @@ def execute(
         show_axis=True,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/clustering/kmeans_calculator.py b/fezrs/tools/clustering/kmeans_calculator.py
index 7061675..3b92b0e 100644
--- a/fezrs/tools/clustering/kmeans_calculator.py
+++ b/fezrs/tools/clustering/kmeans_calculator.py
@@ -101,10 +101,12 @@ def execute(
         show_axis=False,
         colormap=None,
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -117,4 +119,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/filters/gaussian_calculator.py b/fezrs/tools/filters/gaussian_calculator.py
index 060dd23..52e3b8f 100644
--- a/fezrs/tools/filters/gaussian_calculator.py
+++ b/fezrs/tools/filters/gaussian_calculator.py
@@ -35,10 +35,12 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=False,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -51,4 +53,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/filters/laplacian_calculator.py b/fezrs/tools/filters/laplacian_calculator.py
index dd030a3..d0dc0f8 100644
--- a/fezrs/tools/filters/laplacian_calculator.py
+++ b/fezrs/tools/filters/laplacian_calculator.py
@@ -64,10 +64,12 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=False,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -80,4 +82,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/filters/mean_calculator.py b/fezrs/tools/filters/mean_calculator.py
index 9500e9a..5585e1e 100644
--- a/fezrs/tools/filters/mean_calculator.py
+++ b/fezrs/tools/filters/mean_calculator.py
@@ -33,10 +33,12 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=False,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -49,4 +51,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/filters/median_calculator.py b/fezrs/tools/filters/median_calculator.py
index 861449d..7fdc8aa 100644
--- a/fezrs/tools/filters/median_calculator.py
+++ b/fezrs/tools/filters/median_calculator.py
@@ -64,10 +64,12 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=False,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -80,4 +82,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/filters/sobel_calculator.py b/fezrs/tools/filters/sobel_calculator.py
index 14ba79d..8edd838 100644
--- a/fezrs/tools/filters/sobel_calculator.py
+++ b/fezrs/tools/filters/sobel_calculator.py
@@ -68,10 +68,12 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=False,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -84,4 +86,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/glcm/glcm_calculator.py b/fezrs/tools/glcm/glcm_calculator.py
index cfd5551..df20ac6 100644
--- a/fezrs/tools/glcm/glcm_calculator.py
+++ b/fezrs/tools/glcm/glcm_calculator.py
@@ -220,7 +220,7 @@ def execute(
         show_axis=False,
         colormap=None,
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/hsv/hsv_calculator.py b/fezrs/tools/hsv/hsv_calculator.py
index b97af42..eb7f952 100644
--- a/fezrs/tools/hsv/hsv_calculator.py
+++ b/fezrs/tools/hsv/hsv_calculator.py
@@ -68,10 +68,12 @@ def execute(
         show_axis=True,
         colormap=None,
         show_colorbar=True,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=False,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -84,4 +86,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/hsv/irhsv_calculator.py b/fezrs/tools/hsv/irhsv_calculator.py
index aa7ef24..a922ee7 100644
--- a/fezrs/tools/hsv/irhsv_calculator.py
+++ b/fezrs/tools/hsv/irhsv_calculator.py
@@ -67,10 +67,12 @@ def execute(
         show_axis=True,
         colormap=None,
         show_colorbar=True,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=False,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -83,4 +85,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/image_enhancement/adaptive_calculator.py b/fezrs/tools/image_enhancement/adaptive_calculator.py
index 3d9a725..8089048 100644
--- a/fezrs/tools/image_enhancement/adaptive_calculator.py
+++ b/fezrs/tools/image_enhancement/adaptive_calculator.py
@@ -75,7 +75,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=True,
diff --git a/fezrs/tools/image_enhancement/adaptive_rgb_calculator.py b/fezrs/tools/image_enhancement/adaptive_rgb_calculator.py
index 0ec9545..7e64827 100644
--- a/fezrs/tools/image_enhancement/adaptive_rgb_calculator.py
+++ b/fezrs/tools/image_enhancement/adaptive_rgb_calculator.py
@@ -91,7 +91,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=True,
diff --git a/fezrs/tools/image_enhancement/equalize_calculator.py b/fezrs/tools/image_enhancement/equalize_calculator.py
index 5b60b0a..df948ff 100644
--- a/fezrs/tools/image_enhancement/equalize_calculator.py
+++ b/fezrs/tools/image_enhancement/equalize_calculator.py
@@ -67,7 +67,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/image_enhancement/equalize_rgb_calculator.py b/fezrs/tools/image_enhancement/equalize_rgb_calculator.py
index 80a2a95..c34fd31 100644
--- a/fezrs/tools/image_enhancement/equalize_rgb_calculator.py
+++ b/fezrs/tools/image_enhancement/equalize_rgb_calculator.py
@@ -91,7 +91,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=True,
diff --git a/fezrs/tools/image_enhancement/float_calculator.py b/fezrs/tools/image_enhancement/float_calculator.py
index 768c4f6..20567f4 100644
--- a/fezrs/tools/image_enhancement/float_calculator.py
+++ b/fezrs/tools/image_enhancement/float_calculator.py
@@ -58,7 +58,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=True,
diff --git a/fezrs/tools/image_enhancement/gamma_calculator.py b/fezrs/tools/image_enhancement/gamma_calculator.py
index c305e81..3c18e01 100644
--- a/fezrs/tools/image_enhancement/gamma_calculator.py
+++ b/fezrs/tools/image_enhancement/gamma_calculator.py
@@ -82,7 +82,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/image_enhancement/gamma_rgb_calculator.py b/fezrs/tools/image_enhancement/gamma_rgb_calculator.py
index c18a832..5e49e82 100644
--- a/fezrs/tools/image_enhancement/gamma_rgb_calculator.py
+++ b/fezrs/tools/image_enhancement/gamma_rgb_calculator.py
@@ -87,7 +87,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=True,
diff --git a/fezrs/tools/image_enhancement/log_adjust_calculator.py b/fezrs/tools/image_enhancement/log_adjust_calculator.py
index fb112e6..69d1438 100644
--- a/fezrs/tools/image_enhancement/log_adjust_calculator.py
+++ b/fezrs/tools/image_enhancement/log_adjust_calculator.py
@@ -75,7 +75,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/image_enhancement/original_calculator.py b/fezrs/tools/image_enhancement/original_calculator.py
index d1c6eff..3dbb181 100644
--- a/fezrs/tools/image_enhancement/original_calculator.py
+++ b/fezrs/tools/image_enhancement/original_calculator.py
@@ -66,7 +66,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=True,
diff --git a/fezrs/tools/image_enhancement/original_rgb_calculator.py b/fezrs/tools/image_enhancement/original_rgb_calculator.py
index b1dd47d..ab564de 100644
--- a/fezrs/tools/image_enhancement/original_rgb_calculator.py
+++ b/fezrs/tools/image_enhancement/original_rgb_calculator.py
@@ -83,7 +83,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=True,
diff --git a/fezrs/tools/image_enhancement/sigmoid_adjust_calculator.py b/fezrs/tools/image_enhancement/sigmoid_adjust_calculator.py
index c858af2..90dd035 100644
--- a/fezrs/tools/image_enhancement/sigmoid_adjust_calculator.py
+++ b/fezrs/tools/image_enhancement/sigmoid_adjust_calculator.py
@@ -78,7 +78,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/import_tools/__init__.py b/fezrs/tools/import_tools/__init__.py
index 92d7eed..c7aabf5 100644
--- a/fezrs/tools/import_tools/__init__.py
+++ b/fezrs/tools/import_tools/__init__.py
@@ -1,2 +1,2 @@
-from .geoeye_calculator import Geoeye_Calculator
-from .landsat8_calculator import Landsat8_Calculator
+from .geoeye_calculator import Geoeye_Calculator, GeoeyeCalculator
+from .landsat8_calculator import Landsat8_Calculator, Landsat8Calculator
diff --git a/fezrs/tools/import_tools/geoeye_calculator.py b/fezrs/tools/import_tools/geoeye_calculator.py
index 24a0efe..bedac34 100644
--- a/fezrs/tools/import_tools/geoeye_calculator.py
+++ b/fezrs/tools/import_tools/geoeye_calculator.py
@@ -34,7 +34,7 @@ def execute(
         show_axis=True,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
@@ -55,3 +55,8 @@ def execute(
             nrows,
             ncols,
         )
+
+
+# PEP 8 conformant alias; the underscored name is retained for compatibility
+# with existing code and remains exported.
+GeoeyeCalculator = Geoeye_Calculator
diff --git a/fezrs/tools/import_tools/landsat8_calculator.py b/fezrs/tools/import_tools/landsat8_calculator.py
index 901fc0b..afb0211 100644
--- a/fezrs/tools/import_tools/landsat8_calculator.py
+++ b/fezrs/tools/import_tools/landsat8_calculator.py
@@ -74,7 +74,7 @@ def execute(
         show_axis=False,
         colormap=None,
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
@@ -95,3 +95,8 @@ def execute(
             nrows,
             ncols,
         )
+
+
+# PEP 8 conformant alias; the underscored name is retained for compatibility
+# with existing code and remains exported.
+Landsat8Calculator = Landsat8_Calculator
diff --git a/fezrs/tools/mosaic/__init__.py b/fezrs/tools/mosaic/__init__.py
index 73fba6f..727ddee 100644
--- a/fezrs/tools/mosaic/__init__.py
+++ b/fezrs/tools/mosaic/__init__.py
@@ -1 +1 @@
-from .mosaic_calculator import BaseTool
+from .mosaic_calculator import MosaicCalculator
diff --git a/fezrs/tools/mosaic/mosaic_calculator.py b/fezrs/tools/mosaic/mosaic_calculator.py
index bf82ae4..396259b 100644
--- a/fezrs/tools/mosaic/mosaic_calculator.py
+++ b/fezrs/tools/mosaic/mosaic_calculator.py
@@ -40,7 +40,7 @@ def _export_file(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=100,
         bbox_inches="tight",
         grid=False,
@@ -71,7 +71,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=100,
         bbox_inches="tight",
         grid=False,
diff --git a/fezrs/tools/pca/pca_calculator.py b/fezrs/tools/pca/pca_calculator.py
index 7274b63..8c9497c 100644
--- a/fezrs/tools/pca/pca_calculator.py
+++ b/fezrs/tools/pca/pca_calculator.py
@@ -1,3 +1,4 @@
+import warnings
 from uuid import uuid4
 
 import matplotlib.pyplot as plt
@@ -20,7 +21,22 @@ def __init__(
         swir1_path: BandPathType,
         swir2_path: BandPathType,
         selectBand: BandNamePCAType | None = None,
+        component: int | None = None,
+        standardize: bool = False,
     ):
+        """
+        Args:
+            component: Principal component to inspect, numbered 1..6 in order of
+                decreasing explained variance.
+            selectBand: Deprecated. A band name that resolves to a fixed
+                component index. A principal component is a linear combination
+                of all six input bands, so no component corresponds to an input
+                band; use ``component`` instead.
+            standardize: Run PCA on the correlation matrix rather than the
+                covariance matrix, by scaling each band to unit variance first.
+                Without it, bands with the largest digital-number range dominate
+                the leading components regardless of their information content.
+        """
         super().__init__(
             red_path=red_path,
             green_path=green_path,
@@ -47,7 +63,7 @@ def __init__(
             self.metadata_bands["red"]["width"],
         )
 
-        self.selectBand = selectBand
+        self.standardize = standardize
 
         # Input band order.
         #
@@ -62,6 +78,40 @@ def __init__(
             "green": 5,
         }
 
+        self.band_order = [
+            name
+            for name, _ in sorted(
+                self.bindTheBandsToNumber.items(), key=lambda item: item[1]
+            )
+        ]
+
+        if component is not None and selectBand is not None:
+            raise ValueError("Pass either 'component' or 'selectBand', not both.")
+
+        if selectBand is not None:
+            if selectBand not in self.bindTheBandsToNumber:
+                raise ValueError(f"Invalid PCA band: {selectBand}")
+            resolved = self.bindTheBandsToNumber[selectBand] + 1
+            warnings.warn(
+                f"PCACalculator's 'selectBand' is deprecated: {selectBand!r} "
+                f"resolves to principal component {resolved}. A principal "
+                "component is a linear combination of all six input bands, so "
+                "no component corresponds to an input band. Pass "
+                f"component={resolved} instead.",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+            component = resolved
+
+        if component is not None and not 1 <= component <= 6:
+            raise ValueError(
+                f"component must be between 1 and 6, received {component}."
+            )
+
+        self.component = component
+        self.selectBand = selectBand
+        self._pca = None
+
     def _validate(self):
         """
         Validate the input raster bands before performing PCA.
@@ -100,11 +150,10 @@ def _validate(self):
                 f"Missing required PCA bands: {missing_bands}"
             )
 
-        if self.selectBand is not None:
-            if self.selectBand not in self.bindTheBandsToNumber:
-                raise ValueError(
-                    f"Invalid PCA band: {self.selectBand}"
-                )
+        if self.component is not None and not 1 <= self.component <= 6:
+            raise ValueError(
+                f"component must be between 1 and 6, received {self.component}."
+            )
 
     def process(self):
         """
@@ -173,11 +222,32 @@ def process(self):
                 "No valid pixels were found for PCA."
             )
 
+        valid_images = images[valid_mask]
+
+        if self.standardize:
+            # Correlation-matrix PCA. sklearn decomposes the covariance matrix,
+            # which lets whichever band happens to carry the widest
+            # digital-number range dominate the leading components regardless of
+            # how much information it holds.
+            band_std = valid_images.std(axis=0)
+            band_std[band_std == 0] = 1.0
+            valid_images = (valid_images - valid_images.mean(axis=0)) / band_std
+
         pca = skpc(n_components=6)
 
-        transformed_valid = pca.fit_transform(
-            images[valid_mask]
-        )
+        transformed_valid = pca.fit_transform(valid_images)
+
+        # Eigenvector signs are arbitrary: the same scene can yield an inverted
+        # component image between runs, or between a scene and a crop of it,
+        # which makes results non-reproducible and the imagery hard to read.
+        # Fix the convention so the largest-magnitude loading is always
+        # positive.
+        dominant = np.argmax(np.abs(pca.components_), axis=1)
+        signs = np.sign(pca.components_[np.arange(6), dominant])
+        signs[signs == 0] = 1.0
+
+        pca.components_ = pca.components_ * signs[:, np.newaxis]
+        transformed_valid = transformed_valid * signs
 
         transformed = np.full(
             (images.shape[0], 6),
@@ -197,6 +267,43 @@ def process(self):
 
         return self._output
 
+    @property
+    def explained_variance_ratio_(self):
+        """
+        Share of total variance carried by each principal component.
+
+        Returns:
+            np.ndarray: Shape ``(6,)``, ordered by decreasing variance.
+
+        Raises:
+            RuntimeError: If ``process()`` has not run yet.
+        """
+        if self._pca is None:
+            raise RuntimeError(
+                "Run process() before reading explained_variance_ratio_."
+            )
+        return self._pca.explained_variance_ratio_
+
+    @property
+    def components_(self):
+        """
+        Eigenvector loadings, shape ``(6, 6)`` as ``(component, band)``.
+
+        Band order is given by ``band_order``. These loadings, not the variance
+        share, are what identify a useful component: a target is isolated by the
+        component in which the relevant bands carry high loadings of opposing
+        sign.
+
+        Signs follow a fixed convention (largest-magnitude loading positive), so
+        repeated runs and crops of the same scene are directly comparable.
+
+        Raises:
+            RuntimeError: If ``process()`` has not run yet.
+        """
+        if self._pca is None:
+            raise RuntimeError("Run process() before reading components_.")
+        return self._pca.components_
+
     def _customize_export_file(self, ax):
         pass
 
@@ -212,10 +319,10 @@ def histogram_export(
     ):
         
 
-        if self.selectBand is None:
+        if self.component is None:
             raise ValueError(
-                "You cannot use histogram_export() without "
-                "passing selectBand."
+                "You cannot use histogram_export() without passing component "
+                "(or the deprecated selectBand)."
             )
 
         self._validate()
@@ -223,9 +330,7 @@ def histogram_export(
         if not hasattr(self, "_output"):
             self.process()
 
-        component_index = self.bindTheBandsToNumber[
-            self.selectBand
-        ]
+        component_index = self.component - 1
 
         pca_component = self._output[component_index]
 
@@ -239,9 +344,10 @@ def histogram_export(
             color="black",
         )
 
+        # Labelling this by an input band name attributed the output to a band
+        # that did not produce it: every component mixes all six inputs.
         ax.set_title(
-            f"Histogram of PCA Band "
-            f"{self.selectBand.capitalize()}"
+            f"Histogram of Principal Component {self.component}"
         )
 
         if title:
@@ -249,7 +355,7 @@ def histogram_export(
                 f"{title}-FEZrs"
             )
 
-        ax.set_xlabel("PCA Value")
+        ax.set_xlabel(f"PC{self.component} Value")
         ax.set_ylabel("Density")
         ax.grid(grid)
 
@@ -275,7 +381,7 @@ def _export_file(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=False,
@@ -364,7 +470,7 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=True,
diff --git a/fezrs/tools/spectral_indices/afri_calculator.py b/fezrs/tools/spectral_indices/afri_calculator.py
index 39d8f00..07a8143 100644
--- a/fezrs/tools/spectral_indices/afri_calculator.py
+++ b/fezrs/tools/spectral_indices/afri_calculator.py
@@ -105,10 +105,12 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=True,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=True,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -121,4 +123,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/spectral_indices/bi_calculator.py b/fezrs/tools/spectral_indices/bi_calculator.py
index 77b90eb..8f57490 100644
--- a/fezrs/tools/spectral_indices/bi_calculator.py
+++ b/fezrs/tools/spectral_indices/bi_calculator.py
@@ -138,10 +138,12 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=True,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=True,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -154,4 +156,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/spectral_indices/ndvi_calculator.py b/fezrs/tools/spectral_indices/ndvi_calculator.py
index 494ff5e..080fd00 100644
--- a/fezrs/tools/spectral_indices/ndvi_calculator.py
+++ b/fezrs/tools/spectral_indices/ndvi_calculator.py
@@ -42,10 +42,12 @@ def execute(
         show_axis=False,
         colormap=cm.Grays,
         show_colorbar=True,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=True,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -58,4 +60,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/spectral_indices/ndwi_calculator.py b/fezrs/tools/spectral_indices/ndwi_calculator.py
index bdda774..4ca5af6 100644
--- a/fezrs/tools/spectral_indices/ndwi_calculator.py
+++ b/fezrs/tools/spectral_indices/ndwi_calculator.py
@@ -42,10 +42,12 @@ def execute(
         show_axis=False,
         colormap=cm.Grays,
         show_colorbar=True,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=True,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -58,4 +60,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/spectral_indices/savi_calculator.py b/fezrs/tools/spectral_indices/savi_calculator.py
index ce9a48b..5b5b937 100644
--- a/fezrs/tools/spectral_indices/savi_calculator.py
+++ b/fezrs/tools/spectral_indices/savi_calculator.py
@@ -39,10 +39,12 @@ def execute(
         show_axis=False,
         colormap="gray",
         show_colorbar=True,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=True,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -55,4 +57,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/spectral_indices/ui_calculator.py b/fezrs/tools/spectral_indices/ui_calculator.py
index 06f4405..ce9f139 100644
--- a/fezrs/tools/spectral_indices/ui_calculator.py
+++ b/fezrs/tools/spectral_indices/ui_calculator.py
@@ -42,10 +42,12 @@ def execute(
         show_axis=False,
         colormap=cm.gray,
         show_colorbar=True,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=True,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -58,4 +60,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/spectral_profile/spectral_profile_calculator.py b/fezrs/tools/spectral_profile/spectral_profile_calculator.py
index 29535e2..29f952a 100644
--- a/fezrs/tools/spectral_profile/spectral_profile_calculator.py
+++ b/fezrs/tools/spectral_profile/spectral_profile_calculator.py
@@ -104,10 +104,12 @@ def execute(
         show_axis=True,
         colormap="gray",
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=1000,
         bbox_inches="tight",
         grid=True,
+        nrows=None,
+        ncols=None,
     ):
         return super().execute(
             output_path,
@@ -120,4 +122,6 @@ def execute(
             dpi,
             bbox_inches,
             grid,
+            nrows,
+            ncols,
         )
diff --git a/fezrs/tools/svm/__init__.py b/fezrs/tools/svm/__init__.py
new file mode 100644
index 0000000..9f65257
--- /dev/null
+++ b/fezrs/tools/svm/__init__.py
@@ -0,0 +1 @@
+from .svm_calculator import SVMCalculator
diff --git a/fezrs/tools/svm/svm_calculator.py b/fezrs/tools/svm/svm_calculator.py
index 69a598e..4fe3d18 100644
--- a/fezrs/tools/svm/svm_calculator.py
+++ b/fezrs/tools/svm/svm_calculator.py
@@ -152,7 +152,7 @@ def _export_file(
         show_axis=True,
         colormap=None,
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
@@ -182,7 +182,7 @@ def execute(
         show_axis=True,
         colormap=None,
         show_colorbar=False,
-        filename_prefix="Tool_output",
+        filename_prefix=None,
         dpi=500,
         bbox_inches="tight",
         grid=False,
diff --git a/paper/paper.md b/paper/paper.md
index 87964ac..4536827 100644
--- a/paper/paper.md
+++ b/paper/paper.md
@@ -106,7 +106,7 @@ FEZrs was built to address this fragmentation by consolidating frequently used r
 
 # Software design
 
-FEZrs is organized around a shared abstract base class (`BaseTool`) that standardizes the lifecycle of every analysis module: input validation, processing, visualization customization, and export. Each calculator (for example, `NDVICalculator`, `GaussianCalculator`, or `KMeansCalculator`) inherits this interface, accepts band file paths through a common file-handling layer, and exposes a small set of methods such as `execute` and `chart_export`. This pattern keeps the public API uniform across spectral indices, filters, enhancement tools, change-detection utilities, and machine-learning modules, reducing cognitive overhead when composing multi-step workflows.
+FEZrs is organized around a shared abstract base class (`BaseTool`) that standardizes the lifecycle of every analysis module: input validation, processing, visualization customization, and export. Each calculator (for example, `NDVICalculator`, `GaussianCalculator`, or `KMeansCalculator`) inherits this interface, accepts band file paths through a common file-handling layer, and exposes a small set of methods such as `execute` and `histogram_export`. This pattern keeps the public API uniform across spectral indices, filters, enhancement tools, change-detection utilities, and machine-learning modules, reducing cognitive overhead when composing multi-step workflows.
 
 The package is modular by domain: (`spectral_indices`, `filters`, `image_enhancement`, `change_detection`, `clustering`, `glcm`, `pca`, `svm`, and others), while shared utilities handle band-path typing, file I/O, and histogram support. Raster inputs are typically multi-band geospatial imagery. Outputs are written as figures and processed products suitable for inspection, reporting, and further analysis. The design deliberately favors composition of independent calculators over a single monolithic pipeline object, so researchers can select only the methods required for a given study while still benefiting from consistent validation and export behavior.
 
diff --git a/tests/base_test.py b/tests/base_test.py
index b6a3094..605e67f 100644
--- a/tests/base_test.py
+++ b/tests/base_test.py
@@ -1,3 +1,5 @@
+from pathlib import Path
+
 import numpy as np
 import pytest
 
@@ -90,3 +92,87 @@ def test_execute_returns_self():
     result = tool.execute(".")
 
     assert result is tool
+
+
+# --- Export arguments that were accepted and then ignored (issue #42) ---------
+
+
+def test_export_file_honours_filename_prefix(tmp_path):
+    """
+    filename_prefix was accepted by all 37 calculators, forwarded correctly, and
+    then overwritten on the first line of _export_file() before it was used.
+    """
+    tool = DummyExportTool()
+    tool._output = np.array([[1, 2], [3, 4]])
+
+    filename = tool._export_file(tmp_path, filename_prefix="my_run")
+
+    assert Path(filename).name.startswith("my_run_output_")
+
+
+def test_export_file_defaults_to_the_tool_name(tmp_path):
+    """Omitting the prefix must keep the previous default filenames."""
+    tool = DummyExportTool()
+    tool._output = np.array([[1, 2], [3, 4]])
+
+    filename = tool._export_file(tmp_path)
+
+    assert Path(filename).name.startswith("Dummy_output_")
+
+
+def test_execute_forwards_nrows_and_ncols():
+    """
+    nrows/ncols were declared and documented on execute() but never reached
+    _export_file(), so a multi-panel layout was silently ignored.
+    """
+    captured = {}
+
+    class RecordingTool(BaseTool):
+        def __init__(self):
+            self._output = np.array([[1]])
+
+        def _validate(self):
+            pass
+
+        def process(self):
+            pass
+
+        def _export_file(self, *args, **kwargs):
+            captured["args"] = args
+            return "out.png"
+
+    RecordingTool().execute(".", nrows=2, ncols=3)
+
+    # positional tail of _export_file(...) is (..., grid, nrows, ncols)
+    assert captured["args"][-2:] == (2, 3)
+
+
+def test_execute_defaults_nrows_and_ncols_to_single_panel():
+    captured = {}
+
+    class RecordingTool(BaseTool):
+        def __init__(self):
+            self._output = np.array([[1]])
+
+        def _validate(self):
+            pass
+
+        def process(self):
+            pass
+
+        def _export_file(self, *args, **kwargs):
+            captured["args"] = args
+            return "out.png"
+
+    RecordingTool().execute(".")
+
+    assert captured["args"][-2:] == (1, 1)
+
+
+def test_export_file_produces_the_requested_grid(tmp_path):
+    tool = DummyExportTool()
+    tool._output = np.array([[1, 2], [3, 4]])
+
+    filename = tool._export_file(tmp_path, nrows=1, ncols=1)
+
+    assert Path(filename).is_file()
diff --git a/tests/docs_imports_test.py b/tests/docs_imports_test.py
new file mode 100644
index 0000000..fd1b119
--- /dev/null
+++ b/tests/docs_imports_test.py
@@ -0,0 +1,107 @@
+"""
+Execute every import statement that appears in the documentation.
+
+Issue #42 found 13 of 23 documented import lines failing, from five distinct
+causes -- two of them packaging bugs rather than documentation errors. This test
+extracts the import lines from `docs/`, the README and the paper, and runs them,
+so documentation and package layout cannot drift apart again.
+"""
+
+import re
+from pathlib import Path
+
+import pytest
+
+PROJECT_ROOT = Path(__file__).resolve().parents[1]
+
+DOC_SOURCES = (
+    sorted((PROJECT_ROOT / "docs").glob("*.md"))
+    + [PROJECT_ROOT / "README.md"]
+    + sorted((PROJECT_ROOT / "paper").glob("*.md"))
+)
+
+IMPORT_PATTERN = re.compile(
+    r"^\s*(from fezrs[\w.]* import [\w\s,()]+?|import fezrs[\w.]*)\s*$",
+    re.MULTILINE,
+)
+
+
+def _documented_imports():
+    found = []
+    for source in DOC_SOURCES:
+        if not source.is_file():
+            continue
+        for match in IMPORT_PATTERN.finditer(source.read_text()):
+            statement = " ".join(match.group(1).split())
+            found.append(pytest.param(statement, id=f"{source.name}::{statement}"))
+    return found
+
+
+DOCUMENTED_IMPORTS = _documented_imports()
+
+
+def test_documentation_contains_import_examples():
+    """Guards against the extraction silently matching nothing."""
+    assert len(DOCUMENTED_IMPORTS) >= 15
+
+
+@pytest.mark.parametrize("statement", DOCUMENTED_IMPORTS)
+def test_documented_import_works(statement):
+    exec(statement, {})
+
+
+def test_every_exported_calculator_is_listed_in_the_readme():
+    """
+    The README listed 28 calculators while the package exported 37, omitting the
+    entire change-detection group and SVM.
+    """
+    import fezrs
+
+    readme = (PROJECT_ROOT / "README.md").read_text()
+
+    exported = [name for name in fezrs.__all__ if name.endswith("Calculator")]
+    # The underscored legacy names stay exported but the README documents the
+    # PEP 8 aliases they point at.
+    documented = [name for name in exported if "_" not in name]
+
+    missing = [name for name in documented if f"`{name}`" not in readme]
+
+    assert not missing, f"calculators exported but absent from README: {missing}"
+
+
+def test_subpackages_expose_their_calculators():
+    """
+    change_detection/ and svm/ had no __init__.py, so nothing could be imported
+    from either, and mosaic/__init__.py re-exported BaseTool instead of
+    MosaicCalculator.
+    """
+    from fezrs.tools.change_detection import BurnCalculator  # noqa: F401
+    from fezrs.tools.mosaic import MosaicCalculator
+    from fezrs.tools.svm import SVMCalculator  # noqa: F401
+
+    assert MosaicCalculator.__name__ == "MosaicCalculator"
+
+
+def test_media_package_is_importable():
+    """
+    fezrs/media/ holds the watermark but had no __init__.py, so
+    find_packages(include=["fezrs", "fezrs.*"]) in setup.py skipped it.
+    """
+    import fezrs.media
+
+    assert fezrs.media is not None
+
+
+def test_setup_find_packages_collects_every_tool_subpackage():
+    setuptools = pytest.importorskip("setuptools")
+    find_packages = setuptools.find_packages
+
+    packages = set(find_packages(include=["fezrs", "fezrs.*"]))
+
+    for required in (
+        "fezrs.media",
+        "fezrs.tools.change_detection",
+        "fezrs.tools.svm",
+        "fezrs.tools.mosaic",
+    ):
+        assert required in packages, f"{required} would not be packaged"
diff --git a/tests/tools/image_enhancement/float_calculator_test.py b/tests/tools/image_enhancement/float_calculator_test.py
index 1ac18c1..ec9290c 100644
--- a/tests/tools/image_enhancement/float_calculator_test.py
+++ b/tests/tools/image_enhancement/float_calculator_test.py
@@ -194,7 +194,7 @@ def test_execute_with_default_parameters(mock_float_calculator):
         False,
         "gray",
         False,
-        "Tool_output",
+        None,
         500,
         "tight",
         True,
diff --git a/tests/tools/import_tools/geoeye_calculator_test.py b/tests/tools/import_tools/geoeye_calculator_test.py
index 76fa566..bdfaef6 100644
--- a/tests/tools/import_tools/geoeye_calculator_test.py
+++ b/tests/tools/import_tools/geoeye_calculator_test.py
@@ -133,7 +133,7 @@ def test_execute_with_default_parameters(mock_geoeye_calculator):
         True,
         "gray",
         False,
-        "Tool_output",
+        None,
         500,
         "tight",
         False,
diff --git a/tests/tools/import_tools/landsat8_calculator_test.py b/tests/tools/import_tools/landsat8_calculator_test.py
index 21cccd8..02b0745 100644
--- a/tests/tools/import_tools/landsat8_calculator_test.py
+++ b/tests/tools/import_tools/landsat8_calculator_test.py
@@ -248,7 +248,7 @@ def test_execute_with_default_parameters(mock_landsat8_calculator):
         False,
         None,
         False,
-        "Tool_output",
+        None,
         500,
         "tight",
         False,
diff --git a/tests/tools/mosaic/mosaic_calculator_test.py b/tests/tools/mosaic/mosaic_calculator_test.py
index 659474d..6c64568 100644
--- a/tests/tools/mosaic/mosaic_calculator_test.py
+++ b/tests/tools/mosaic/mosaic_calculator_test.py
@@ -276,7 +276,7 @@ def test_execute_with_default_parameters(mock_mosaic_calculator):
         False,
         "gray",
         False,
-        "Tool_output",
+        None,
         100,
         "tight",
         False,
diff --git a/tests/tools/pca/pca_calculator_test.py b/tests/tools/pca/pca_calculator_test.py
index ba59942..9ba6490 100644
--- a/tests/tools/pca/pca_calculator_test.py
+++ b/tests/tools/pca/pca_calculator_test.py
@@ -173,13 +173,13 @@ def test_process_pixels_are_samples_not_bands(mock_pca_calculator):
     assert np.linalg.matrix_rank(centered_bands) <= N_BANDS - 1
 
 
-def test_histogram_export_requires_select_band(mock_pca_calculator):
+def test_histogram_export_requires_a_component(mock_pca_calculator):
     mock_pca_calculator.selectBand = None
+    mock_pca_calculator.component = None
 
     with pytest.raises(
         ValueError,
-        match="You cannot use histogram_export\\(\\) without "
-        "passing selectBand\\.",
+        match="without passing component",
     ):
         mock_pca_calculator.histogram_export(
             output_path="./output"
@@ -255,3 +255,146 @@ def test_execute(mock_pca_calculator):
 
     assert result is mock_pca_calculator
     mock_execute.assert_called_once()
+
+
+# --- Component selection and eigen-structure (issue #42) ----------------------
+
+
+def _synthetic_pca_calculator(component=None, selectBand=None, standardize=False):
+    """
+    Build a PCACalculator over six correlated synthetic bands, with
+    BaseTool.__init__ patched out so nothing touches disk.
+    """
+    rng = np.random.default_rng(11)
+    base = rng.normal(size=(16, 16))
+    bands = [
+        base * weight + rng.normal(scale=0.2, size=(16, 16))
+        for weight in (1.0, 0.8, 0.6, 1.4, 1.2, 0.4)
+    ]
+    # Deliberately unequal band variances, so covariance and correlation PCA
+    # give different answers.
+    bands[3] = bands[3] * 40.0
+
+    handler = MagicMock()
+    handler.get_metadata_bands.return_value = {
+        name: {"height": 16, "width": 16, "image_skimage": bands[0]}
+        for name in ("nir", "blue", "green", "red", "swir1", "swir2")
+    }
+    handler.get_images_collection.return_value = bands
+
+    def fake_init(self, *args, **kwargs):
+        self.files_handler = handler
+        self._output = None
+
+    with patch("fezrs.tools.pca.pca_calculator.BaseTool.__init__", fake_init):
+        return PCACalculator(
+            red_path="red.tif",
+            green_path="green.tif",
+            blue_path="blue.tif",
+            nir_path="nir.tif",
+            swir1_path="swir1.tif",
+            swir2_path="swir2.tif",
+            component=component,
+            selectBand=selectBand,
+            standardize=standardize,
+        )
+
+
+def test_component_selects_a_principal_component():
+    calculator = _synthetic_pca_calculator(component=3)
+
+    assert calculator.component == 3
+
+
+@pytest.mark.parametrize("component", [0, 7, -1])
+def test_component_must_be_within_range(component):
+    with pytest.raises(ValueError, match="component must be between 1 and 6"):
+        _synthetic_pca_calculator(component=component)
+
+
+def test_select_band_is_deprecated_and_names_its_component():
+    """
+    selectBand='red' plotted the first principal component and titled the figure
+    "Histogram of PCA Band Red", attributing the output to an input band that
+    did not produce it.
+    """
+    with pytest.warns(DeprecationWarning, match="resolves to principal component 1"):
+        calculator = _synthetic_pca_calculator(selectBand="red")
+
+    assert calculator.component == 1
+
+
+def test_component_and_select_band_are_mutually_exclusive():
+    with pytest.raises(ValueError, match="not both"):
+        _synthetic_pca_calculator(component=2, selectBand="red")
+
+
+def test_explained_variance_ratio_is_exposed():
+    calculator = _synthetic_pca_calculator(component=1)
+
+    with pytest.raises(RuntimeError, match="Run process\\(\\)"):
+        calculator.explained_variance_ratio_
+
+    calculator.process()
+
+    ratios = calculator.explained_variance_ratio_
+    assert ratios.shape == (6,)
+    np.testing.assert_allclose(ratios.sum(), 1.0, atol=1e-6)
+    # Ordered by decreasing variance.
+    assert np.all(np.diff(ratios) <= 1e-12)
+
+
+def test_components_loadings_are_exposed():
+    calculator = _synthetic_pca_calculator(component=1)
+
+    with pytest.raises(RuntimeError, match="Run process\\(\\)"):
+        calculator.components_
+
+    calculator.process()
+
+    assert calculator.components_.shape == (6, 6)
+    assert len(calculator.band_order) == 6
+
+
+def test_component_signs_are_deterministic():
+    """
+    Eigenvector signs are arbitrary in PCA, so without a fixed convention the
+    same scene can produce an inverted component image between runs -- a
+    reproducibility defect of the same kind as issue #37.
+    """
+    first = _synthetic_pca_calculator(component=1)
+    second = _synthetic_pca_calculator(component=1)
+
+    first.process()
+    second.process()
+
+    np.testing.assert_allclose(first.components_, second.components_)
+    np.testing.assert_allclose(first._output, second._output)
+
+    # The convention itself: the largest-magnitude loading is positive.
+    dominant = np.argmax(np.abs(first.components_), axis=1)
+    leading = first.components_[np.arange(6), dominant]
+    assert np.all(leading > 0)
+
+
+def test_standardize_changes_the_variance_structure():
+    """
+    sklearn decomposes the covariance matrix, so a band with a much wider
+    digital-number range dominates the leading components regardless of its
+    information content. Standardizing scales each band to unit variance first.
+    """
+    covariance = _synthetic_pca_calculator(component=1, standardize=False)
+    correlation = _synthetic_pca_calculator(component=1, standardize=True)
+
+    covariance.process()
+    correlation.process()
+
+    assert not np.allclose(
+        covariance.explained_variance_ratio_,
+        correlation.explained_variance_ratio_,
+    )
+    # The inflated band no longer swamps PC1.
+    assert (
+        correlation.explained_variance_ratio_[0]
+        < covariance.explained_variance_ratio_[0]
+    )
diff --git a/tests/tools/spectral_indices/afri_calculator_test.py b/tests/tools/spectral_indices/afri_calculator_test.py
index 6813175..2d3f284 100644
--- a/tests/tools/spectral_indices/afri_calculator_test.py
+++ b/tests/tools/spectral_indices/afri_calculator_test.py
@@ -124,6 +124,8 @@ def test_execute_calls_base_execute(mock_afri_calculator):
         500,
         "tight",
         False,
+        None,
+        None,
     )
     assert result == "executed"
 
@@ -142,9 +144,11 @@ def test_execute_with_default_parameters(mock_afri_calculator):
         False,
         "gray",
         True,
-        "Tool_output",
+        None,
         1000,
         "tight",
         True,
+        None,
+        None,
     )
     assert result == "executed"
diff --git a/tests/tools/spectral_indices/bi_calculator_test.py b/tests/tools/spectral_indices/bi_calculator_test.py
index 430fce8..b4183f5 100644
--- a/tests/tools/spectral_indices/bi_calculator_test.py
+++ b/tests/tools/spectral_indices/bi_calculator_test.py
@@ -124,6 +124,8 @@ def test_execute_calls_base_execute(mock_bi_calculator):
         500,
         "tight",
         False,
+        None,
+        None,
     )
     assert result == "executed"
 
@@ -142,9 +144,11 @@ def test_execute_with_default_parameters(mock_bi_calculator):
         False,
         "gray",
         True,
-        "Tool_output",
+        None,
         1000,
         "tight",
         True,
+        None,
+        None,
     )
     assert result == "executed"
diff --git a/tests/tools/spectral_indices/ndvi_calculator_test.py b/tests/tools/spectral_indices/ndvi_calculator_test.py
index 56c8239..5cd1dcb 100644
--- a/tests/tools/spectral_indices/ndvi_calculator_test.py
+++ b/tests/tools/spectral_indices/ndvi_calculator_test.py
@@ -129,6 +129,8 @@ def test_execute_calls_base_execute(mock_ndvi_calculator):
         500,
         "tight",
         False,
+        None,
+        None,
     )
     assert result == "executed"
 
@@ -147,9 +149,11 @@ def test_execute_with_default_parameters(mock_ndvi_calculator):
         False,
         cm.Grays,
         True,
-        "Tool_output",
+        None,
         1000,
         "tight",
         True,
+        None,
+        None,
     )
     assert result == "executed"
diff --git a/tests/tools/spectral_indices/ndwi_calculator_test.py b/tests/tools/spectral_indices/ndwi_calculator_test.py
index cb55a4e..0b9965b 100644
--- a/tests/tools/spectral_indices/ndwi_calculator_test.py
+++ b/tests/tools/spectral_indices/ndwi_calculator_test.py
@@ -129,6 +129,8 @@ def test_execute_calls_base_execute(mock_ndwi_calculator):
         500,
         "tight",
         False,
+        None,
+        None,
     )
     assert result == "executed"
 
@@ -147,9 +149,11 @@ def test_execute_with_default_parameters(mock_ndwi_calculator):
         False,
         cm.Grays,
         True,
-        "Tool_output",
+        None,
         1000,
         "tight",
         True,
+        None,
+        None,
     )
     assert result == "executed"
diff --git a/tests/tools/spectral_indices/savi_calculator_test.py b/tests/tools/spectral_indices/savi_calculator_test.py
index 62c3141..97eac4f 100644
--- a/tests/tools/spectral_indices/savi_calculator_test.py
+++ b/tests/tools/spectral_indices/savi_calculator_test.py
@@ -117,6 +117,8 @@ def test_execute_calls_base_execute(mock_savi_calculator):
         500,
         "tight",
         False,
+        None,
+        None,
     )
     assert result == "executed"
 
@@ -135,9 +137,11 @@ def test_execute_with_default_parameters(mock_savi_calculator):
         False,
         "gray",
         True,
-        "Tool_output",
+        None,
         1000,
         "tight",
         True,
+        None,
+        None,
     )
     assert result == "executed"
diff --git a/tests/tools/spectral_indices/ui_calculator_test.py b/tests/tools/spectral_indices/ui_calculator_test.py
index 596d04a..07abd99 100644
--- a/tests/tools/spectral_indices/ui_calculator_test.py
+++ b/tests/tools/spectral_indices/ui_calculator_test.py
@@ -129,6 +129,8 @@ def test_execute_calls_base_execute(mock_ui_calculator):
         500,
         "tight",
         False,
+        None,
+        None,
     )
     assert result == "executed"
 
@@ -147,9 +149,11 @@ def test_execute_with_default_parameters(mock_ui_calculator):
         False,
         cm.gray,
         True,
-        "Tool_output",
+        None,
         1000,
         "tight",
         True,
+        None,
+        None,
     )
     assert result == "executed"
diff --git a/tests/tools/spectral_profile/spectral_profile_calculator_test.py b/tests/tools/spectral_profile/spectral_profile_calculator_test.py
index 67721fa..5577918 100644
--- a/tests/tools/spectral_profile/spectral_profile_calculator_test.py
+++ b/tests/tools/spectral_profile/spectral_profile_calculator_test.py
@@ -208,6 +208,8 @@ def test_execute_calls_base_execute(mock_spectral_profile_calculator):
         500,
         "tight",
         False,
+        None,
+        None,
     )
     assert result == "executed"
 
@@ -226,10 +228,12 @@ def test_execute_with_default_parameters(mock_spectral_profile_calculator):
         True,
         "gray",
         False,
-        "Tool_output",
+        None,
         1000,
         "tight",
         True,
+        None,
+        None,
     )
     assert result == "executed"
 
diff --git a/tests/tools/svm/svm_calculator_test.py b/tests/tools/svm/svm_calculator_test.py
index 777ee9a..485f38b 100644
--- a/tests/tools/svm/svm_calculator_test.py
+++ b/tests/tools/svm/svm_calculator_test.py
@@ -187,7 +187,7 @@ def test_execute_with_default_parameters(mock_svm_calculator):
         True,
         None,
         False,
-        "Tool_output",
+        None,
         500,
         "tight",
         False,