Hello,
my question regards the different treatment of embedded profiles in PhotoShopElements13 and RT 5.2.
I have 2 images from my scanner created from the same scan. Both were saved by the scan program in Adobe RGB colour space. One has no profile embedded, the other has the Adobe RGB profile embedded (the program provides this choice). Both images are identical on the pixel level, when I subtract them in imageJ. When I open them in PSE and save them again as Adobe RGB the images are again identical (PSE was set up to interpret the embedded profile in both cases). However, If I open these images in RT using the default profile (i.e. “use embedded profile” in the colour management tab) with no changes applied whatsoever, the images come out different.
@Jossie to get an answer worth anything we must see the files in question:
Resize the scanned images in your scanning software to something small and easy to download, e.g. 100x100px (or just scan a patch at that size), one with the embedded profile and one without, and upload both using some lossless file sharing service like https://filebin.net/
When I open them in PSE and save them again as Adobe RGB
An image is developed in RT and saved with ICC-profile RT_sRGB. If I open this developed image in RT it looks the same as the original image during development. This is what I expect. However, if I open the developed image in PhotoShopElements (set up to apply the embedded ICC-profile and convert to AdobeRGB) the image comes out differently. The colours are faded.
I am completely confused about the different treatment of embedded ICC-profiles by the various programs.
I am not sure if this is due to the different monitor profiles. I am using an EIZO and EIZO states that one should not associate the monitor profile on the operating system level, since the profile would then be applied twice. As far as I understand the profile LUT is directly loaded into the monitor. But I am not very familiar with these things. That is why I ask.
I think this is what’s happening.
When you open the tif with profile embedded, RT sees it and all is ok.
When you open the other one i.e. no profile, with “Use embedded if possible”, then of course RT doesn’t know it’s adobeRGB, so I reckon it assumes sRGB. I think this is confirmed because I opened the no-profile one in Gimp, assigned sRGB, output to jpeg, and it was the same image as the RT one, by flicking between the files using the built in Ubuntu viewer “Image Viewer”, which I believe obeys profiles, so no risk of RT monitor profile issues muddying the waters, because not using RT (or Gimp) to make the comparison.
RawTherapee’s profile RT_Medium_gsRGB is the equivalent of Adobe RGB but it does not exactly match the profile embedded in Dia_4850_HDR_withICC.tif
To make sure we’re using the same Adobe RGB profile (yes they can differ, sRGB profiles can differ a lot from each other as well) I extracted the profile from Dia_4850_HDR_withICC.tif using: exiftool -icc_profile -b -w icc Dia_4850_HDR_withICC.tif
and I saved it as ADBE.icc
You’re opening two identical images in PSE, except one has a profile assigned and the other does not, then you’re saving them both “as” Adobe RGB which I guess means that you assign the Adobe RGB profile to them. Identical pixel values in, identical pixel values out, both get the Adobe RGB profile assigned, they both match.
When you open Dia_4850_HDR_noICC.tif in RawTherapee, the “Use embedded, if possible” input profile option finds no input profile and falls back to assuming that your image is in the sRGB colorspace. If you set ADBE.icc in RT as both the input profile and the output profile, then the saved result perfectly matches the files saved by PSE.
So now I understand the difference comes from the fact that RT falls back to sRGB, if no profile is found. This explains the difference. Yes, I have seen that sRGB profiles are not all the same.
But one thing is still strange. As I had written earlier today, opening the image developed in RT again in RT gives the same colours as during development, which is what one expects. Opening this image developed in RT with RT_sRG embedded in PSE does give different colours. Only if I turn off colour management in PSE (i.e. it ignores the embedded profile) I do get the same colours as in RT. Does this mean, that RT somehow knows that the image was already developed and is in RT_sRGB (meaning nothing is to be done), whereas PSE does not realize this and applies the embedded profile again, which ruins the colours?
