Stray light (flare) documentation pages
Introduction: Intro to stray light testing and normalized stray light | Outputs from Imatest stray light analysis | History
Background: Examples of stray light | Root Causes | Test overview | Test factors | Test Considerations | Glossary
Calculations: Metric image | Normalization methods | Light source mask methods | Summary Metrics | Analysis Channels | Saturation
Instructions: High-level Imatest analysis instructions (Master and IT) | Computing normalized stray light with Imatest | Motorized Gimbal instructions
Settings: Settings list and INI keys/values | Standards and Recommendations | Configuration file input
Page Contents
This page describes the analysis channel options.
Channel Groups
Channel groups describe which groups of channels to analyze.
| Name | # Input Channels | Description | Additional Settings | |
|---|---|---|---|---|
| Automatic | Any | Automatically choose what analysis channels to use based on the provided image(s).
| 0 | None |
| Each Channel | Any | Analyze each input channel | 1 | None |
| RGB | 3 | Analyze each of the three provided channels as red, green, blue. | 2 | RGB Order |
| Monochrome | 1 | Analyze the single provided channel as monochrome. | 3 | None |
| Statistics | Any | Analyze a statistic (mean, median) of all provided channels. | 4 | Statistics Method |
| Luminance | 3 | Analyze the luminance channel. | 5 | RGB Order, Luminance Weights |
| RGB + Luminance | 3 | Analyze the three (red, green, blue) channels and the computed luminance channel. | 6 | RGB Order, Luminance Weights |
| Single Channel | Any | Analyze a single image channel as specified by the 1-based channel index | 7 | Channel Index |
Additional Settings
Luminance Channels
The luminance channel is calculated by applying weights to each of the red, green, and blue channels:
\(\text{Luminance} = w_{red}\cdot \text{Red} + w_{green} \cdot \text{Green} + w_{blue} \cdot \text{Blue} \)
See the new settings section for the available luminance options.
Statistics Channels
Analyze a statistic of the channels in the image.
The following statistics are available:
| Name | INI Value | Notes |
|---|---|---|
| Mean | 0 | The mean of the provided channels. |
| Median | 1 | The median of the provided channels. |
RGB Order
The RGB identifies how the red, green, and blue channels are ordered in the image.
Channel Index
The channel index is the one-based index of the channel.
For example, for RGB data, Red = 1, Green = 2, and Blue = 3.
Notes
Coloring and Data Labeling
The choice of analysis channels controls how the data are labeled and colored in plots and results.
Image/Settings Mismatches
Imatest will not run if there is a mismatch between the selected settings and the provided image (e.g., trying to analyze a monochrome image as RGB or Luminance, each of which requires three input channels).
Module Specific Notes
Stray Light Notes
Normalization Factor Analysis Channel
For Direct Reference Image and Lambertian Reference Image normalization, if the Channel Group is Luminance or RGB + Luminance, then the Luminance channel of the reference image is used. Otherwise, the Mean of the reference image is used.
Masking Analysis Channel
When producing a mask, if the Channel Group is Luminance or RGB + Luminance, then the Luminance channel of the image is used. Otherwise, the Mean of the image is used. This mask is then applied to each of the analysis channels.