W3C home > Mailing lists > Public > www-style@w3.org > July 2008

Re: [css3-color] ICC implementation

From: David Woolley <forums@david-woolley.me.uk>
Date: Sun, 13 Jul 2008 00:12:35 +0100
Message-ID: <48793A63.7010400@david-woolley.me.uk>
To: www-style@w3.org
CC: Chris Murphy <lists@colorremedies.com>

Chris Murphy wrote:
> 

> An image with no encoding ("gamma 1.0") or linear encoding would look 
> completely washed out. I think it would be obvious to anyone with vision 
> that there is a serious problem so I'm not sure how big of a problem 
> this really could be unless people just aren't paying attention.

Example of images that are clearly gamma 1.0, and have been for several 
years, in spite of my pointing out the problem, and their being 
obviously wrong, supplied off list.

> I know if no camera that does this. Digital cameras all do have linear 
> response to light, and record it that way. The raw data is processed in 
> the camera, tone mapped where it has a tone reproduction curve defined 
> by either the sRGB curve or gamma 2.2, and is then JPEG compressed and 
> tagged with EXIF data as to its color space.

Example of image which is clearly gamma 1.0, but has metadata (as 
decoded by Wikipedia) claiming sRGB colour space also provided off list. 
  This example is from a Panasonic camera.  Although it is possible that 
the image was retouched without correcting the metadata, all the 
indications are that this image wasn't retouched, and I would expect an 
image to be deliberately retouched to gamma 1.0, except for deliberate 
effect.

More generally, the number of images with bad gamma on the web, 
particularly non-professional ones, is sufficiently high that I think 
there must be quite a few digital cameras which don't correct to sRGB, 
although many may well either not specify a colour space, or identify it 
correctly.  I don't think all can be attributed to scanners, which are 
also quite likely to produce gamma 1.0 images in untrained hands.

(On the other hand, both my current Olympus and my very first, Jenoptic, 
do correct to sRGB, although the Jenoptic doesn't provide metadata and 
I'm not sure whether the Olympus encodes colour space.)

I've not quoted the first URL because it belongs to a small organisation 
with which I'm sympathetic, and don't want to criticise it publicly. 
The other is on Wikipedia, but I've extended the same courtesy.  If 
anyone else wants to know the actual examples, ask me off list.

-- 
David Woolley
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RFC1855 says there should be an address here, but, in a world of spam,
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Received on Saturday, 12 July 2008 23:11:22 GMT

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