Gamma 2.2 test pattern suggestion

[tomczak]

Having test patterns right within PWP is nice. There is at least one more that I think would be useful - Gamma check. There is a few of them that I've used and liked:

http://www.normankoren.com/makingfinepr ... gammachart
http://www.normankoren.com/makingfinepr ... gamma_3lvl
http://www.lagom.nl/lcd-test/gamma_calibration.php
http://glennmessersmith.com/images/adjust.htm

I particularly like the one in the last link and I believe that Glenn attached a Creative Commons licence to it, for non-commercial use (a note: you need to download it and look at it in 1:1, not in the browser) - the only problem for same could be that it seems to be using the straight-line gamma segment of sRGB at the for the darkest parts. There are others. Any would do.

The other one, but that's just my idea, would be a sharpening/blurring testing pattern - I use it to figure out what sharpening/blurring sliders and options do. I came up with this one, and it seems to show me what's going on typically...

viewtopic.php?f=5&t=1051

[jsachs]

I tried the gamma test images on two of my calibrated monitors and they did not work, indicating a gamma of roughly 1.2. I don't think this method of checking gamma is reliable for all monitors although I do remember using something similar on CRTs in the old days.

On doing some more testing, it turns out the problem comes from not viewing the gamma test image at 1:1 as the browser was rescaling it.

I added a sharpening test pattern for the next release.

[tomczak]

Many thanks!

This 1:1 viewing of gamma images - even though I know they need to be viewed this way to be effective, it was just yesterday that I forgot and couldn't figure it out for a while what was wrong with either them or my monitor. Nothing was wrong, they just weren't displayed in 1:1...

There is one more image that I thought was probably even more important than gamma for spot-checking if your monitor (or maybe the ambient light) doesn't cheat you too much: they go by different names e.g. black level and white saturation, but basically check how well can your monitor (and you) distinguish between v. dark and black and v. light and white. One should be able to get them about right by a combination what's normally called contrast and brightness.

There are several tests, but some of them are too permissive.

Here is an example of both such test images that are strict:
http://www.lagom.nl/lcd-test/black.php
http://www.lagom.nl/lcd-test/white.php

I tend to use my miniaturised test pattern to quickly check it (left top corner and the ramps below)

https://www.jonathansachs.me/phpbbBB3/v ... f=5&t=2244

[tomczak]

I think I found a way of producing the Black Point and White Level saturation test images fairly quickly within PWP.

Use the Checkerboard Transformation (either from Special Effects of Test Pattern groups).

For Black Point:
1) Set Preview border colour to Black
2) Set one Checkerboard colour as pure black (0) and increase the other colour from black up by one pixel value (set the Colour Picker readout to Decimal), observing the preview when you can start barely differentiating the squares.

For White Saturation:
1) Set Preview border colour to White
2) Set one Checkerboard colour as pure white (255) and decrease the other colour from white down by one pixel value, observing the preview when you can start barely differentiating the squares.