Chroma Subsampling in jpeg optimizer

[Dave G]

I've noticed that many of the Chroma subsampling options in the optimizer have no apparent effect on the image and no effect on the file size. What effect there is seems to be reversed from what I expect. Ie the most subsampled option YCnCr 4x4 2x2 2x2 produces the largest file and the best image whereas YCbCr 1x1 1x1 1x1 (none) produces the worst image and the smallest file. That should be the other way around - right?

[Dave G]

And it's not just the optimizer. "Save as" also gets the subsampling backwards with the highest degree of subsampling selected producing larger files with better color in high res color transitions than the (none) option.

This is on X6. (16.2.0.20 X64) It says there are no updates available.