Are gamma visual test images reliable?

[Omelette]

I would like to ask your opinion about gamma visual test images. They never seem to work for me, and I’m starting to wonder if my i1Display Pro is not working properly. I have the same result in all tests and in all displays that I calibrate: the dark tones appear to have lower gamma (around 2.0-2.1). I tried to calibrate to both sRGB and 2.2 gamma, and I’m always using software with full color management to view the test images (XNView, Photoshop, configured Firefox…).

This is one of the visual test images that I’m using, but I also have a few more images downloaded on my computer: http://www.lagom.nl/lcd-test/gamma_calibration.php
48% looks perfect, but 25% and 10% are at 2.1 and 2.0

• This topic was modified 1 year, 10 months ago by Omelette.
• This topic was modified 1 year, 10 months ago by Omelette.

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[Vincent]

If you want to test calibration gamma visually, test are non color managed.
Also due to limited contrast of displays a plot of gama value (Y) vs input signal (X) will bend near black (lower gamma value than desired).

If you wish to test gamma values on color managed enviroments you’ll face similar issues:
-if profile is idealized near black, it won’t store actual value, hence test is invalid
-if profile stores actual non ideal behavior near black, color management engine will need to choose (user config) to clip due to limited contrast or to apply some kind of black compensation, hence bending de gamma vs input plot

TL;DR
What you see is a result of limited contrast displays trying to keep brightness separation between greys while trying to track target gamma.

[Author]

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