sRGB vs 2.2

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This topic contains 5 replies, has 3 voices, and was last updated by  Wire (@wire) 1 week, 6 days ago.

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  • #18927

    J Johnson (@j-johnson)
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    I couldn’t find a good answer via google. Should I be using 2.2 or sRGB when creating my profile? The only major difference I’ve noticed is that the darks have much lower gamma with sRGB. I think I want the setting that matches more closely with what people see, which I assume is 2.2.

    But, what is your thought? Which is more common, and does the less common option have any advantages?

    #18929

    J Johnson (@j-johnson)
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    Nevermind. I found the answer, and basically sRGB is meant for CRTs. I’m going to redo my calibrations using 2.2.

    #19130

    Wire (@wire)
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    The reason you didn’t get an answer is that the entire context of the question is nonsensical…

    sRGB is effectively gamma 2.2. So you should get the same tonal results from DisplayCal for sRGB and G2.2.

    If you see a difference, something is going wrong.

    As to CRTs, the concept of gamma is defined and understood in terms of the relationship between our visual response of lightness and the physics of CRTs, because the origin of electronic displays is about television. sRGB -> G2.2 is a compromise of television and computer graphics tonal response. The only way to understand why this is so is to recount the history of color science, TV and computers.  Super complex.

    For people just getting started with DisplayCal,  its best to simply your environment to a decision of whether you are primarily interested in web or video.

    If web, you want sRGB.

    If video you want Rec.709, which is sRGB with G2.4.

    If your display has settings pertaining to either of these options, make your choice and select these before running DispkayCal.

    This is an oversimplification, but the place to start.

    If you have a high-gamut display or UHDTV you’re in a whole other realm.  Try to simplify, if you can, by setting your display per above until you can learn more about the implications which depend on many factors.

    #19142

    Florian Höch (@fhoech)
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    sRGB is effectively gamma 2.2. So you should get the same tonal results from DisplayCal for sRGB and G2.2.

    No. As noted by the OP, sRGB has a linear segment near black, so in a color managed environment, if you assign a Rec. 709 “pure” gamma 2.2 profile to an sRGB image, you’ll see darker near-black tones (and vice versa).

    #19146

    Wire (@wire)
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    Yes I am aware of the distinction but felt it was a distraction to mention it.

    For most users the effect will not be visible.

    For anyone who cares, with access to Photoshop, you can see for yourself.

    Take the Adobe-supplied sRGB which is a true one with the split (sRGB IEC61966-2.1) and set Edit > Color Settings > Working RGB to it. Then use the same setting again but choose Custom RGB . This will create a “simplified” sRGB version using gamma 2.2.  Save it.

    Now get a black patch test image like you can find at lagom.nl/lcdtest into photoshop and assign the true sRGB to it, then assign or soft proof the simplified sRGB. It you can tell the diff I will be very surprised.

    You can demonstrated there is a diff by taking the black patch test, duplicating it and assigning one true sRGB and assigning the other simplified sRGB and converting to true sRGB and overlaying the two versions in difference mode to see a barely discernible diff is present. This diff can be enhanced using a Levels adjustment layer.

    If ordinary users can see the diff between true sRGB and G2.2 profiles in their photo work I will be dumbfounded to hear it! Tho no doubt there are golden eyes out there.

    In my experience if the orginal poster, based on the way he posed his question and conclusion can see a diff, something else has gone wrong.

    Also doesn’t Rec.709 use a split curve too?

    The conventional wisdom is these splits are attributable to the limits of arithmetic units in embedded microprocessors for early digi devices, and according to C. Poynton in his Gamma FAQ using a linear-light segment at bottom end help control sensor noise in early designs. Both sound plausible to me.

    #19147

    Wire (@wire)
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    I am wrong 🙂

    I take back what I just said about discernabke differences between true sRGB and G2.2. I just went through the exercise I described in prev post and softproofing G2.2 against true sRGB creates a readily visibke diff!

    So I am wrong according to my own logic

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