GIMP export to sRGB doesn’t match up to the original colorspace. https://photos.app.goo.gl/H88CHi9JyD94n6yT9 Here’s a wedding bouquet, in three images. Only the JPG straight from the RAW processor (I use ASP3) matches the image correctly.
BACKGROUND:
My normal workflow is (1) processing RAW in ASP3, (2) export to TIFF ProPhotoRGB, (3) make last minute edits in GIMP, (4) print from GIMP using TurboPrint (Canon Pro100 or Epson P800). Works great. All the color profiles match up perfectly from a color registered monitor to the final print.
If I replace step (4) with export into JPG from GIMP, the colors shift. I’ve given a link above to three flower images, and only the one that isn’t touched by GIMP is correct.
My workstation is Ubuntu 16.04, GIMP is 2.9.9
Any ideas would be appreciated
UPDATE: Following the suggestions of respondents, I’ve updated to 18.04 and am running 2.10.x. The bug was reported as resolved, and, sure enough, everything is good.
Apparently, GIMP is hardwired for sRGB. For reference on 2.9x versus 2.10x:
If you really do want to edit in color spaces other than sRGB, my patched version of GIMP 2.9 (“GIMP-CCE”) allows you to edit in any well-behaved RGB working space. However, please be aware that default GIMP has quite a lot of functionality that I’ve removed from GIMP-CCE.
The difference appears to be not color, but tone. I can take the “odefinedcolorspace” image and make it equivalent to the others with a simple “reverse gamma” power curve. I can’t look at the profiles’ TRCs, but I’d bet there’s a difference…
Elle Stone weighed in on her insights, and examined the converted outputs (and also noted the odd gamma curve). She, also, encouraged testing in GIMP 2.10.
GIMP 2.10 made no difference. Which made no sense, so I decided to use a text editor and discovered that the converted image still had the ProPhotoRGB profile definition. I ran the export again, and disabled EXIF, XMP and IPTC.
It’s all good, now. The images load just fine for web use.
Not going to disagree. What I can say, is that when I chose to leave those values blank in the export, no profile text was written into the image. Web architecture pretty much defaults to sRGB, so it’s a win, even if it’s a workaround.
Agreed. I will open a ticket on the incident. The information is pretty detailed, and I was fortunate to work directly with Elle Stone on identifying the root cause.
The funny thing is, as far as I know, ALL photo printers from the Canon Pro100 on up can take wide color profiles. It took me a while to line everything up. I use TurboPrint, and imported ProPhotoRGB into the drivers list of color profiles. My primary printer is an Epson P800. I defer to the earlier DPREVIEW topic if anyone is wondering whether or not it matters when printing, and the technical issues.