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Stray light (flare) documentation pages

Introduction: Intro to stray light testing and normalized stray lightOutputs from Imatest stray light analysis | History

Background: Examples of stray lightRoot Causes | Test overview | Test factors | Test ConsiderationsGlossary

Calculations: Metric image calculationsNormalization methodsLight source mask methods | Summary Metrics | Analysis Channels

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 provides a description of the analysis channel options.

Channel Groups

Channel groups describe which groups of channels to analyze.

Name# Input ChannelsDescription INI Value
AutomaticAnyAutomatically choose what analysis channels to use based on the provided image(s).
  • If input data has 1 channel → Monochrome
  • Otherwise → Each Channel
Each ChannelAnyAnalyze each input channel1
RGB3Analyze each of the three provided channels as red, green, blue.2
Monochrome1Analyze the single provided channel as monochrome.3
MeanAnyAnalyze the mean of all provided channels.4
Luminance3Analyze the luminance channel. Data are assumed to be 3 channel in (red, green, blue) order.5
RGB + Luminance3Analyze the three (red, green, blue) channels and the computed luminance channel.6

Luminance Channels

The luminance channel is calculated by applying weights to each of the red, green, and blue channels:

\(\text{Luminance} = w_{red}\cdot \text{Red} + w_{green} \cdot \text{Green} + w_{blue} \cdot \text{Blue} \)

The following weights are available for computing a luminance channel:

NameRedGreenBlueINI Value
IEC 61966-2-10.2126 0.71520.07221
ITU-R BT.601-70.2990.5870.1142


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.