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There are actually two gammas: (1)
encoding gamma, which relates scene luminance to image file pixel levels, and
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display gamma, which relates image file pixel levels to display luminance.
The above two equations (and most references to gamma on this page) refer to encoding gamma. Exceptions are for characterizing color spaces and when display gamma is explicitly referenced, as in the Appendix on Monitor gamma.
The overall system contrast is the product of the encoding and decoding gammas. More generally, we think of gamma as contrast.
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The chart on the right is designed for a visual measurement of display gamma. But it rarely displays correctly in web browsers (and may never display correctly on this Atlassian page, where there is no way to set it to 100% size). It has to be displayed in the monitor’s native resolution, 1 monitor pixel to 1 image pixel. Unfortunately, operating system scaling settings and browser magnifications can make it difficult.  |
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To view the gamma chart (on the right) correctly, right-click on it, copy it, then paste it into Fast Stone Image Viewer.
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Although a full monitor calibration (which requires a spectrophotometer) is recommended for serious imaging work, good results can be obtained by adjusting the monitor gamma to the correct value. We won’t discuss the process in detail, except to note that we have had good luck with Windows systems using QuickGamma.
Appendix II: Tonal response, gamma, and related quantities
For completeness, we’ve updated and kept this table from elsewhere on the (challenging to navigate) Imatest website.
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