File talk:Canon 15mm f2.8 SSC lens and satchel ( DSF3158).jpg

Considerations on Usage of Adobe PhotoShop with Adobe RGB as default Colour Profile

The first image I had uploaded was a little too dark. That amazed me as I had racked up the exposure value of the (purposefully) underexposed images enough to attain a more or less white, and definitely not grey, background.

Prior Information

• Beginning this week I reset my workflow within Adobe PhotoShop to "Adobe RGB" as default colour space, not "sRGB" as before. Of course, prior to this step I had read numerous articles on the pros and cons.
  • All those knowledgeable undoubtedly state that files saved with Adobe RGB values and which are erraneously rendered via sRGB are depicted with mostly muted and darker colours.
  • But this is manageable. In theory, yes. But there are some caveats, especially regarding Wiki Commons, as I will now report.
• Processing within PhotoShop is always 16 bit and all processing levels are saved as PSD or PSB files.
• As I usually do, I saved the so processed image via "save as" as a JPG file. This has always worked fine for me, of course previously with sRGB.
• Uploaded the resulting file to Wiki Commons without having a closer look.
• The resulting image as depicted by Firefox for Wikimedia is visibly too dark, by about -0.75 exposure values (in PhotoShop speak).
• The same image drawn directly from my computer is by far brighter. Not quite as bright as within PhotoShop, but only off by a margin of -0.35 exposure values.

Presumed Improvement

• Well, after more reading I discovered that, now in 2019, all major browsers respect ICC colour profiles embedded within image files and do not simply convert colour values to sRGB.
• How embed a ICC colour profile? Adobe PhotoShop offers this feature within the "export" function, something I hadn't used before.
  • Deactivated sRGB, activated "embed ICC colour profile".
• Eureka! All images are now much brighter than the above created JPG file (by "save as"), shown via Firefox browser and/or Irfan View. Still not quite the brightness level within PhotoShop, but quite near, i. e. approximately -0.25 exposure values.
• Uploaded this new image with hopeful expectations.

Inexplicable Effect

• That second image I had just uploaded should have been visibly brighter than the first image. But is wasn't. It was even darker!
• Shown side by side via two Firefox browser instances, the very same newly uploaded image showed this peculiar behaviour:
  • Firefox instance 1: the new image loaded straight from my computer is just -0.25 exposure values darker than Photoshop. It seems that Firefox has recognised the ICC colour profile and that this profile has thus contributed to the final appearance on screen.
  • Firefox instance 2: the same image loaded from Wiki Commons is almost -1.00 exposure values darker than Photoshop.
• As seen above, whenever Firefox recognises an ICC profile it will utilise it to render the appearance on screen.
• Thus I come to the conclusion that either (a) the Wiki Commons upload process eradicates or deactivates the ICC profile or (b) the image information forwarded to the browser (here Firefox) seems to be lacking ICC colour profile information, so that Firefox interprets the colour values by default as sRGB, which renders them too dark (see Prior Information).

Remedy

• I don't yet have a remedy for this situation, except that I will try to convert to sRGB on exporting files.
• As this seems a general problem, I just wanted to jot a short note on my hitherto efforts should anyone else take interest in the subject.
• I will let you know the outcome of my attempts (and of further research into the subject) here on this talk page.

--Franz van Duns (talk) 14:06, 19 July 2019 (UTC)

Enhanced Brightness before "Saving As"

• Hmm, no improvement.
• The file I have just uploaded at 16:40, 19 July 2019 was modified as such:
  • Raised exposure level by +0.51 in Adobe Photoshop before explicitly setting to sRGB colour space and "saving as" JPG.
• The EXIF data of this file state:
  • Color Space: Uncalibrated
  • ICC Profile Name: Adobe RGB (1998)
• This new image should definitely be brighter. But, nope, it is still rather dark, much the same as the other two images.
• Another try ...

--Franz van Duns (talk) 16:51, 19 July 2019 (UTC)

Additions to above statement:

• My above remark "Hmm, no improvement" was my first impression based on the small preview files.
• When I reloaded (!!) the Wiki Commons page, the enhanced brightness was much more pronounced.

Enhanced Brightness before again "Saving As"

• Yes, much better. But 'll do some further comparisons between various states of this image before adding to this statement.

--Franz van Duns (talk) 17:11, 19 July 2019 (UTC)

• Reloaded page with preview images.
  • Result: Now one can see the enhanced brightness of the 4th upload as compared to the 3rd.
  • This was not visible before. Seemingly the first preview shown after an upload is a duplicate of the previously uploaded image.
• Such a pity I didn't make a screenshot before reloading the page containing the 4 preview images.
• I will continue to investigate in this astonishing affair.

--Franz van Duns (talk) 17:18, 19 July 2019 (UTC)