Commons talk:Featured picture candidates

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Awareness of color space data in files[edit]


Recently, Colin was kind enough to tell me that I had no embedded color space metadata in a recent FPC nomination and in another file I had uploaded. To be frank, I had only little technical knowledge on the topic of the RGB color space, and I was not convinced it was important. However, after re-reading a chapter about color management in "The Digital Negative" by Jeff Schewe and threads such as User talk:Diliff#color space and User talk:Benh#color space I am beginning to understand what the consequences are from not having a properly defined color space in the Exif image metadata and an embedded color profile. Looking through my own workflow, I found with the help of Colin and Bawolff that a script I was using to mitigate a mediawiki metadata viewer bug stripped off the embedded color profile data in the process. During the weekend I have now inspected my recent uploads using the excellent Jeffrey Freidl's Exif (Image Metadata) Viewer. I found that 40 files among those 4 FPs(!) had no embedded color profile data. The consequence of that is that applications reading the file for display or print may be in doubt how to convert the jpg data into color information giving an ambiguity in how the data in the files shall be represented. So what I would see on a properly color calibrated montor could have a completely different appearance on another calibrated monitor if another browser or application was used to read and interprete the jpg!

I have now corrected my script (again with the help from Bawolff) and updated the 40 images such that they have proper embedded colour profile metadata. -- Slaunger (talk) 18:05, 6 July 2015 (UTC)

Three out of ten FPC nominations have color space issues![edit]

Out of curiosity I then checked all 62 images against the Exif viewer, which were currently nominated at FPC last night and to my surprise I found that for 18 nominated pictures (about 30%) different kinds of color space errors or warnings were reported by the viewer.

12 nominations had no defined color space nor an embedded color profile. This means that any web browser or application reading these files have to guess how to map the data into colors. Thats bad!. The most usual for web use is to guess these files should use an sRGB color profile with a gamma of 2.2. But if another color profile such as the Adobe RGB color space (suitable for prints) or the large gamut ProPhoto RGB color space is used you would see a completely different picture. Today there may not be a large risk of actual ambiguity as 'sRGB' is a de facto default in most web applications, but as wide-gamut monitors become more prevalent we may see a drift towards wider color spaces than sRGB for web usage in the future. So the ambiguity rises.

3 nominations had an indicated color profile as 'sRGB' but no embedded color profile. This is a less serious error as applications, who knows about sRGB would be capable of interpreting the data correctly. But applications, which do not have a builtin hardcoded knowledge about sRGB would have a problem.

Finally, three nominations used AdobeRGB or ProPhoto RGB color spaces with embedded color profiles. This is good for professional printing and excahnge as these generally conserve more of the original colors captured by the camera, but most web browsers only understand the 'sRGB' color space and does not even attempt to interprete the embedded color profile metadata. Thus the simple applications, cannot render the colors as intended for those jpegs.

I would like to urge nominators to check their nominations against a good exif viewer such as Jeffrey Friedl's prior to nomination to avoid problems arising from missing color space metadata. -- Slaunger (talk) 15:39, 6 July 2015 (UTC)

The problem with space color is maybe because "default" space color in Lightroom is Adobe RGB, it change the quality in the file itself or only the way how we are looking the image?. What is mediawiki viewer bug?. Thanks --The Photographer (talk) 23:27, 6 July 2015 (UTC)
Lightroom is colour managed and can use a wide colourspace internally if your monitor supports it. But on export the default for JPG is sRGB. -- Colin (talk) 14:08, 7 July 2015 (UTC)
The Photographer The mediawiki metadata viewer bug is described in Commons:Village_pump/Archive/2015/04#Error in metadata viewer? and appears to be relevant only for images exported from Lightroom 6.1. The Exif data here are OK, but encoded in a way which is not taken into account by the mediawiki software used to decode the Exif metadata. The problem in that thread was that the exiftools script given there to fix the issue also stripped the color space information and much else usefull inoformation. This has later been corrected in this discussion: User talk:Bawolff#Error in metadata viewer. -- Slaunger (talk) 15:13, 7 July 2015 (UTC)
I corrected most of these. I discovered that Gimp in Windows can't assign a color profile out of the box, and there is no warning about that. Regards, Yann (talk) 07:46, 7 July 2015 (UTC)
Thanks, Yann. Your efforts are appreciated! -- Slaunger (talk) 15:15, 7 July 2015 (UTC)

I think there are two problems. The first is "a little knowledge is a dangerous thing". People look at their camera manual or the export dialog and see there is a colourspace option. They google and learn that AdobeRGB has "more colours" than sRGB (it doesn't, it has the same number of colours but arranged differently) and so assume that AdobeRGB is better. And some pro photographers write books that recommend AdobeRGB -- those guys send their work to print shops, not to the internet! So we end up with images nominated at FP with colourspaces that aren't suitable for the internet. The second problem seems to be that some non-professional image tools like Paint and Gimp seem to make it easy to lose the colourspace information.

I intend to write up some help pages about this, with some images people can use to test their browser. Unfortunately browsers are dumber than we would like and monitors less colourful than we would like. The only reliable way to ensure your image displays with the correct colours is to tag the colourspace and include a profile. But an sRGB image with the relevant colourspace tag set to sRGB is a good start. Having no tag or profile in a JPG is really like having a thermometer with no scale markings. -- Colin (talk) 14:08, 7 July 2015 (UTC)

Question whether I did the right thing[edit]

Regarding the candidate image File:Pont de Chancia02 2015-05-10.jpg, with the command line

exiftool "-icc_profile<=sRGB_IEC61966-2-1_black_scaled.icc" Pont_de_Chancia02_2015-05-10.jpg

I have added a colour profile and uploaded this modified file as a new version. While this probably prevents some software from guessing a wrong gamma curve, I wonder whether this generic profile does best justice to the intensities as recorded with my camera. -- KlausFoehl (talk) 12:52, 7 July 2015 (UTC)

Your out-of-camera JPG is in sRGB but most camera manufacturers don't embed the 4K profile in order to save space. So provided that icc profile you used is a faithful implementation of sRGB it should be ok. There's nothing Canon-specific in an sRGB JPG so no other (e.g. manufacturer's) profile will enable more colours to be seen. However, if you had recorded in raw format, then there are indeed more intense colours possible than sRGB can represent and that can be captured by your camera. But for many image subjects the range of colour intensities falls within sRGB colourspace and for 99.9% of our viewers, their monitor is incapable of even displaying the range of sRGB never mind anything wider. -- Colin (talk) 14:19, 7 July 2015 (UTC)
Short version: You did the right thing! Smile -- Slaunger (talk) 15:16, 7 July 2015 (UTC)

Browser test[edit]

I plan to write some help pages on the issue of colour profiles, etc. As a start, I have prepared a page that demonstrates some issues browsers have with images using (or lacking) various colour profiles. Have a look at

I would appreciate some feedback (particularly from users with Mac desktop computers, since I don't have one) along with the name and version number of browser used, and whether you have a standard-gamut monitor or a wide-gamut monitor along with a wide-gamut profile installed in your OS. It would be interesting to know how many regulars at FP have wide-gamut monitors and also how many have calibrated their monitors (and how many have neither).

Btw, I asked a friend for stats on desktop/mobile usage on Wikipedia. The figures vary between language editions, and not all the necessary information is collected, but it is safe to say that between a third and a half of all Wikipedia traffic is via a mobile browser. There are no mobile browsers that do any colour management at all. The message from that is that if you want people to see your images properly, you need to upload them as sRGB and embed a colour profile. -- Colin (talk) 09:40, 23 July 2015 (UTC)

FP user profiles[edit]

Please indicate your desktop/browser situation.

  • I have a Dell Ultrasharp 2711 wide-gamut monitor that has been calibrated and profiled by an x-rite i1Display Pro colorimeter using dispcalGUI (a graphical front-end to Argyll CMS). I'm using Windows 8.1 and have configured Firefox so that it correctly colour manages all images for the wide-gamut display. -- Colin (talk) 09:40, 23 July 2015 (UTC)
  • The situation on a PC is not so bad. With my old 2011-Acer monitor and computer with Vista, I don't see much differences in images without a color profile, both with Chrome and FF. Regards, Yann (talk) 10:44, 23 July 2015 (UTC)
If your Acer monitor is just a standard-gamut display (most are) then the sRGB images without any profile will look very similar to the ones with a profile. If Windows doesn't have a profile installed for your monitor, it will just use sRGB anyway and so they will appear identical. If you have profiled your standard-gamut monitor with a colorimeter (or installed the manufacturer's ICC/ICM file) then you may see a very subtle difference in the images without an embedded sRGB profile, but it won't be as dramatic as if you had a wide-gamut monitor. -- Colin (talk) 10:54, 23 July 2015 (UTC)

Clearing chronological galley every month[edit]

The chronological gallery need to be cleared by moving contents to parent gallery when one month is over. Hope one or two volunteers will take care of it. Jee 05:32, 18 July 2015 (UTC)

This is something that can and ought to be done by a bot. -- KTC (talk) 14:58, 19 July 2015 (UTC)
Then, please. :) Jee 15:45, 19 July 2015 (UTC)