Re: use of sRGB as a default
Re: use of sRGB as a default
- Subject: Re: use of sRGB as a default
- From: Steve Upton <email@hidden>
- Date: Mon, 21 Jun 2004 13:05:06 -0700
At 8:44 AM -0600 6/21/04, Chris Murphy wrote:
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On Jun 21, 2004, at 12:14 AM, John Zimmerer wrote:
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>Chris,
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>The issue isn't gamut size, it's where certain hues land inside the gamuts. Find an image, like the red bridge reference image, with a vivid blue sky in it, duplicate the image, then assign Generic RGB to one and sRGB to the other. You'll notice the sky is much more purple in sRGB than in Generic RGB.
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All you've demonstrated is that Generic RGB is a more appropriate source profile for this particular image than sRGB. I'm sure I could dig up a whole bunch of ColorMatch RGB images, perform the same "test" and come up with the same "results." How was this image originally created? What platform? What application? Was the display calibrated and profiled? Is it by nature a tagged or an untagged image?
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I still fail to find any of the explanations I've read even remotely compelling as to why Generic RGB is better for untagged images than sRGB - except to compensate for the antiquated legacy display gamma on the Macintosh.
I think that using profiles other than sRGB to tag user images coming from cameras or scanners is not necessarily a bad idea. The standard suggestion, that sRGB is where most cameras aim their color and so is best used as the source profile is not too tough to prove wrong. If Apple comes up with a better generic profile that, when applied to these images, meets user expectations better (on average) then it is probably a good idea. Purple blues and tomato reds are common with sRGB applied to camera images. (at least in my experience)
On the other hand, I do feel that any web browser should stick to web standards and assume sRGB as the source for untagged images. This is the only way we can get consistent color of any sort on the web. Yes, the majority of systems are uncalibrated and unprofiled but they are closer to sRGB and especially gamma 2.2 than probably other choices. More importantly, those who want to get good color on the web TODAY tend to ask for our (collective experts) advice and are advised to convert to sRGB prior to sending images to the web. Those who want to view color as accurately as possible are advised to turn on color management in their browser (if it is available) and calibrate their displays to gamma 2.2 (regardless of the platform they are on). Browsers should respect embedded profiles and use sRGB for untagged images. Developers should follow W3C specs (and information from Apple's own site) regarding specification of color profiles for untagged images.
The challenge I'm sure Apple is facing is that these two ideas do not make for simple consistent behavior. If camera and scanner images are tagged with one profile and web pages with another, the story gets muddied. I personally think it is better in this instance to have a muddy story than force all incoming device images to have sRGB or all incoming web images Generic RGB. I also feel Apple should give us access to change the defaults. So we can set default profiles for web and device images. (I realize some of this exists but some of it does not)
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Suffice to say, for Safari to assume sRGB as source for untagged images would be a good thing if not well overdue considering that's how web browsers are expected to behave per the W3C.
I totally agree.
As for gamma, I think that 2.2 is best for both worlds. For image encoding 2.2 distributes the numbers more inline with human perception and for 8 bit imagery, encoding efficiently is important - especially with grays. For displays, while 1.8 gamma is more in line with the transfer function to print, if images are color managed then it shouldn't make enough of a difference to calibrate Macs differently than everything else. Many, many design / photo creative groups have Macs and Windows-based machines working side-by-side and calibrating them to different standards doesn't make sense it only causes confusion and causes the Macs to stick out as "different" - not a good different. Add to that the fact that web and other non-tagged images are at 2.2 makes me want to view the web at gamma 2.2. The very small possible improvements gained by using gamma 1.8 in either image encoding OR display calibration are just not worth the confusion and incompatibility it causes.
just by 2 cents
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
o email@hidden 206.985.6837
o ColorGear ColorThink ColorValet ColorSmarts ProfileCentral
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