Archives for 2014

It occurred to me that, what with CIEL*a*b* being the reference standard for the ICC color management scheme, that there might be some bias towards minimizing errors measured in Lab built into the Photoshop/ACE  algorithms. Lab is not perceptually uniform, although it tries hard, so things might be worse than they seem when Lab DeltaE is… [Read More]

We got pretty good results with round trip conversions from sRGB to Adobe RGB and back using a smallish 16-bit image and a 16-bit image with all the 8-bit sRGB colors. Before I declare victory, I decided to see what happened with a lot more 16-bit colors. I wrote a Matlab script to generate a… [Read More]

Bruce Lindbloom has another test image on his website: a 16 megapixel image containing all possible RGB colors in an 8-bit per plane RGB space. The image is arranged with the colors in a regular order, so you can see where particular colors of interest are: I brought the image into Photoshop and changes the… [Read More]

[Note: this post has been rewritten to correct an error. The cause of the error was that Bruce Lindbloom’s desk image on his web site is in the sRGB, gamma 2.20 color space, while I thought it was in the sRGB IEC61966-2.1 color space. That caused some rather large errors, which are much smaller once the… [Read More]

There is a persistent legend in the digital photography world that color space conversions cause color shifts and should be avoided unless absolutely necessary.  Fifteen years ago, there were strong reasons for that way of thinking, but times have changed, and I think it’s time to take another look. First off, there are several color… [Read More]