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FAQ: Colour Profiles and You
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rjlittlefield
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PostPosted: Sun Oct 05, 2008 4:07 pm    Post subject: FAQ: Colour Profiles and You Reply with quote

This topic is prompted by recent experiences. At least four times in the past couple of weeks, I have encountered images that were not being displayed in the same colors that the authors intended.

Very briefly, the problem has to do with "color profiles". These are small tables of information that can be embedded in image files. Their intended purpose is to specify what color is supposed to be displayed for particular values of RGB in the file. Many cameras now produce these tables, and most image processing programs know how to use them, but most browsers still just ignore them!

This is a problem because the cameras are using profiles with a wider "gamut" than the profile that is effectively assumed by the browsers. That causes the browsers to display an image with reduced saturation and sometimes color and brightness shifts.

NikonUser has graciously allowed me to illustrate with one of his recent images.



For more illustrations and some discussion, see http://www.northlight-images.co.uk/article_pages/web-browser-color-management.html . There's a bunch more information on the web about this problem, but quite frankly it's so complicated that unless you're a graphics professional there's no point trying to understand it.

The important thing is how to fix it, and that's easy. If your images have profiles, just be sure to convert them to standard RGB before saving out a JPG to put on the web.

In Photoshop CS, you do this with Image | Mode | Convert to Profile... and select sRGB. (It'll probably say "sRGB IEC61966-2.1"). Images that use this profile will display the same way in browsers that they do in Photoshop. (Caution: In Photoshop CS, do not use Image | Mode | Apply Profile... That essentially does what the browsers do, which is exactly what you don't want.)

In Photoshop Elements, I believe the sequence is Image | Convert Color Profile | Apply sRGB Profile. (In Elements, "Apply" actually means "Convert". It's a confusing inconsistency in the user interfaces of Elements and CS.)

The image shown above originally had a profile of "Adobe RGB (1998)". That seems to be fairly common. Don't let the "RGB" fool you. If it's not "sRGB", it's not going to do what you expect.

Note also that it's not a good idea to convert your "keeper" image files to sRGB. There's a reason why cameras are using the wider gamut profiles -- they allow some colors to be represented that sRGB doesn't, which can lead to better reproduction on devices such as high-end printers.

Presumably this problem will disappear at some point in the future when browsers become profile-aware. But people have been saying that for years, and we seem to be only a little closer now than we were when they started.

Hope this helps!

--Rik

Edit: to add warning about Apply Profile in Photoshop CS.


Last edited by rjlittlefield on Tue Aug 24, 2010 12:39 pm; edited 2 times in total
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mgoodm3



Joined: 08 Sep 2008
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PostPosted: Sun Oct 05, 2008 7:14 pm    Post subject: Reply with quote

A big advantage of RAW capture is that there is no color space applied to the image file prior to reconstruction and at least in PShop you can reconstruct into one of 4 profiles wihtout affecting the original.
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rjlittlefield
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PostPosted: Sun Oct 05, 2008 10:03 pm    Post subject: Reply with quote

Good point.

It's quite possible that some of the inappropriate profiles were not injected by the camera itself, but rather by Photoshop during raw conversion.

If you're shooting raw, another solution to the problem is to convert the raw files directly into sRGB as the first step.

However, I'm inclined to recommend against that, on the grounds that it seems safer to use a wide gamut 16-bit format for raw conversion and editing, collapsing only at the very end to 8-bit sRGB for posting. That preserves all your editing work in the broadest range of colors for other media.

--Rik
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mgoodm3



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PostPosted: Mon Oct 06, 2008 7:47 am    Post subject: Reply with quote

I always reconstruct images as a 16 bit and only convert to 8 when I save, but I will apply the color space that applies to the use if the image. Internet (most of my images) go into sRGB. Images for print go into AdobeRGB. The great part about RAW is that you can always go back and do it differently if you wish.

I believe the Adobe Camera Raw uses ProPhotoRGB in its workings which is the largest space of the bunch.
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Cyclops



Joined: 05 Aug 2006
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PostPosted: Fri May 14, 2010 12:08 pm    Post subject: Reply with quote

Useful thread (thanks Rik for pointing me to it!)
Now about RAW, I've never used it as I presumed it was an option to get the best quality for printing and I don't print so never used it. The other problem is my versipn of Elements doesn't recognise the RAW format and the camera, Canon 10D, being old, has no updates available for use in Windows Vista!
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Peter M. Macdonald



Joined: 20 Jan 2009
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PostPosted: Fri May 14, 2010 12:26 pm    Post subject: Reply with quote

Well done Rik - another feather in your cap. An American who can spell colour correctly!

Best,

Peter
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ChrisLilley



Joined: 01 May 2010
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PostPosted: Fri May 14, 2010 12:40 pm    Post subject: Reply with quote

mgoodm3 wrote:
I always reconstruct images as a 16 bit


Sound practice.

mgoodm3 wrote:
I believe the Adobe Camera Raw uses ProPhotoRGB in its workings which is the largest space of the bunch.


I understand that it (and Photoshop) can be told to use that colour space; its not clear to me whether it uses it by default.

ProPhotoRGB is somewhat wasteful in that large amounts of the numerical space is outside the gamut of the human visual system. (This is true for LAB as well, incidentally).

Its quite hard to get good information on the actual gamut of current photographic sensors. I wish I had good data on that.

It is imperative when using a wide-gamut colour space for editing to remain at 16 bits per component. One of the reasons that sRGB was chosen as a default for the Web is that it is (just) possible to squeeze that gamut and that transfer function into 8 bits without objectionable banding.
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ChrisLilley



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PostPosted: Fri May 14, 2010 12:53 pm    Post subject: Re: Colour Profiles and You Reply with quote

rjlittlefield wrote:

In Photoshop CS, you do this with Image | Mode | Convert to Profile... and select sRGB. (It'll probably say "sRGB IEC61966-2.1"). Images that use this profile will display the same way in browsers that they do in Photoshop. (Caution: In Photoshop CS, do not use Image | Mode | Apply Profile... That essentially does what the browsers do, which is exactly what you don't want.)

In Photoshop Elements, I believe the sequence is Image | Convert Color Profile | Apply sRGB Profile. (In Elements, "Apply" actually means "Convert". It's a confusing inconsistency in the user interfaces of Elements and CS.)


That is a sufficiently awful inconsistency that I just reported it to Adobe.

So people reading instructions about what to do in Photoshop, and applying it to Photoshop Elements, will get it exactly wrong. Ouch.
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rjlittlefield
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PostPosted: Fri May 14, 2010 3:24 pm    Post subject: Re: Colour Profiles and You Reply with quote

Peter M. Macdonald wrote:
Well done Rik - another feather in your cap. An American who can spell colour correctly!

Thanks, Peter. Spending so much time on the forum, I hardly notice these differences anymore. My browser does complain about "colour" when I'm typing the body of a posting, but it doesn't spell-check titles. I'm guessing I was in an "colour" mood when I started writing, and then Firefox forced me back to "color" for the body. Oddly enough, as I write this paragraph, my eyes are wondering why Firefox is underlining the wrong ones!

ChrisLilley wrote:
That is a sufficiently awful inconsistency that I just reported it to Adobe.

Thanks, Chris. I presume you have some effective channel for reporting such problems. What is it?

--Rik
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ChrisLilley



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PostPosted: Sat May 15, 2010 2:56 am    Post subject: Reply with quote

Well, lets see if it produces a result before concluding that it is (still) effective. My last contact with the Photoshop team was quite some years ago now.
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Cyclops



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PostPosted: Sat May 15, 2010 4:40 am    Post subject: Reply with quote

Ah I see I have a big problem, because this feature is not part of my early Elements!
This shows the options I have:



No RAW support either it seems so how do I do RAW?
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DQE



Joined: 08 Jul 2008
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PostPosted: Sat May 15, 2010 9:00 am    Post subject: Reply with quote

Cyclops wrote:
Ah I see I have a big problem, because this feature is not part of my early Elements!
This shows the options I have:



No RAW support either it seems so how do I do RAW?


IrfanView is free and with some extra plugins and add-ins, will support raw files - I have verified that it works with Canon 5D and 5DII raw files. You could convert the raw files to tif files and that would be lossless and presumably readable by Photoshop Elements.

I hope this ad-hoc suggestion is helpful. Raw is the only way to go, IMO, for max flexibility and freedom to do the best (lossless) image processing.
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Cyclops



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PostPosted: Sat May 15, 2010 9:05 am    Post subject: Reply with quote

DQE wrote:


IrfanView is free and with some extra plugins and add-ins, will support raw files - I have verified that it works with Canon 5D and 5DII raw files. You could convert the raw files to tif files and that would be lossless and presumably readable by Photoshop Elements.

I hope this ad-hoc suggestion is helpful. Raw is the only way to go, IMO, for max flexibility and freedom to do the best (lossless) image processing.

Yea i have irfanview (Its what i used to do the screengrab)
But if i never make big prints, never need optimum quality, why do i need to shoot in RAW?
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DQE



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PostPosted: Sat May 15, 2010 9:25 am    Post subject: How to enable color management within Firefox 3 Reply with quote

See this URL for instructions on how to enable color/colour management in Firefox 3.

https://developer.mozilla.org/En/ICC_color_correction_in_Firefox

I don't use IE much but seem to recall that it doesn't handle color/colour management as fluently as Firefox 3. Hopefully, someone with knowledge of IE's properties will clarify this issue.

I hope this info is helpful. Failing to manage color profiles properly within one's workflow and/or browser seems likely to cause substantial problems in sharing our photos.

Also, most peoples' monitors don't handle the full 8 bits per channel - they only use 6 bits. I bought an IP LCD monitor instead of a less expensive TN LCD monitor because of these considerations. See this web page for more info:

http://www.clarkvision.com/photoinfo/choosing_an_LCD_monitor/index.html

I believe we should manage our color profiles and color spaces as well as the quality of our monitors in order to obtain good fidelity and reproducibility from our digital cameras and photography.

Also, one can buy calibrated color test patterns and monitor calibration equipment if one wishes to verify that one's camera and monitor are working accurately. Uncalibrated equipment tends to produce unpredictable results!
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Cyclops



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PostPosted: Sat May 15, 2010 9:42 am    Post subject: Reply with quote

Now this is interesting! I did a test and it seems its not a photoshop/web colours issue, but rather theres a discrepancy between Irfanview and Photoshop!
I took an image, did a screen grab using Irfanview of the image when loaded into photoshop elements (PSE) and did another but grabbing the image when loaded into Irfanview, and theres quite a difference! So it would seem that my edition of Photoshop is adding something to the image!


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