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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 | Normalization methodsLight 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 methodologies for computing saturation.

Saturation

Container Max

The Container Max method assumes that the maximum value in the container (data type) is the saturation level.

Data Type Computed Saturation Level [DN]
uint8 255
uint16 65535
uint32 4294967295

 

Caution: This method will fail if the data max is less than the container max, e.g., storing 10 bit/pixel data in a uint16. This failure mode will overestimate the true saturation value.

Image Max

The image max method assumes that the maximum value in the image is the saturation level.

Caution: This method will fail if the image data is less than the saturation level. This failure mode will underestimate the true saturation value.

Note: This is calculated per image. Different scene content may lead to different calculated saturation values.

Image Max (Power Of Two)

The image max (power of two) method attempts to address the failure mode of image max when the maximum value in the image is (slightly) less than saturation. The assumption is that the situation level will be of the form \(2^{N}-1\), where \(N\) is an integer. Under this assumption, the image max is rounded up to the next \(2^{N}-1\).

Image Max (Lower Bound)Image Max (Upper Bound)Calculated Saturation [DN]Calculated Saturation [Bits]
1282552558
256 511 511 9
512 1023 1023 10
1024 2047 2047 11
2048 4095 4095 12
4096 8191 8191 13
8192 16383 16383 14
16384 32767 32767 15
32768 65535 65535 16
65536 131071 131071 17
131072 262143 262143 18
262144 524287 524287 19
524288 1048575 1048575 20
1048576 2097151 2097151 21
2097152 4194303 4194303 22
4194304 8388607 8388607 23
8388608 16777215 16777215 24
16777216 33554431 33554431 25
33554432 67108863 67108863 26
67108864 134217727 134217727 27
134217728 268435455 268435455 28
268435456 536870911 536870911 29
536870912 1073741823 1073741823 30
1073741824 2147483647 2147483647 31
2147483648 4294967295 4294967295 32

Caution: This method will fail if the max of the image data is less than the saturation level. This failure mode will underestimate the true saturation value.

Note: This is calculated per image. Different scene content may lead to different calculated saturation values.

Image Max (Even Power Of Two)

The image max (even power of two) method attempts to address the failure mode of image max when the maximum value in the image is (slightly) less than saturation. The assumption is that the situation level will be of the form \(2^{2n}-1\), where \(n\) is an integer. Under this assumption, the image max is rounded up to the next \(2^{2n}-1\).

Image Max (Lower Bound)Image Max (Upper Bound)Calculated Saturation [DN]Calculated Saturation [Bits]
64 255 255 8
256 1023 1023 10
1024 4095 4095 12
4096 16383 16383 14
16384 65535 65535 16
65536 262143 262143 18
262144 1048575 1048575 20
1048576 4194303 4194303 22
4194304 16777215 16777215 24
16777216 67108863 67108863 26
67108864 268435455 268435455 28
268435456 1073741823 1073741823 30
1073741824 4294967295 4294967295 32

Caution: This method will fail if the max of the image data is less than the saturation level. This failure mode will underestimate the true saturation value.

Note: This is calculated per image. Different scene content may lead to different calculated saturation values.

User-provided Value

This method allows the user to manually enter the saturation value in digital numbers.

Note when known, this or the user-provided bit depth is the recommended method(s).

User-provided Bit Depth

This method allows the user to manually enter the saturation value in bits.

The saturation value is calculated using

\(\mathrm{saturation} = 2^{\mathrm{bit depth}}-1\)

Note when known, this or the user-provided value is the recommended method(s).