Well, for my V2 profiles I wanted the profiles to functionally match ArgyllCMS V2 profiles that have TRCs that require point curves, which have 1024 points, as do most other older “real V2” sRGB ICC profiles. So my decision to use 1024 points (which now I know doesn’t actually happen with my current profile-making code) wasn’t based on “there are standards” but rather on matching existing “real V2” (as opposed to “V2 according to V4 standards”) profiles.
As far as standards go, there are standards for color spaces, such as the sRGB color space. Then there are V2 and V4 ICC specs for making ICC profiles from the color space specs. I don’t recall if the original V2 specs made any such specification as “this many points”, and I don’t recall any such specification in the V4 specs, but in both cases I think it’s not likely that there is such a restriction embedded in the ICC specs.
Regarding the LCMS point profiles with “more points”, didn’t Marti make that change in response to a discussion with the RT devs? The problem was the accuracy with which LCMS makes conversions between V2 point curves. My recollection is that ArgyllCMS (and perhaps other CMMs besides LCMS) interpolates between the points, whereas LCMS quantizes. For example see this thread:
Also see this somewhat related thread, where the problems (especially evident for channel values near zero) with V4 matrix-to-matrix transforms fortunately were subsequently fixed in LCMS (click on “View entire thread” to view the entire thread):
Another way that the RT sRGB “V2” profile differs from older and ArgylCMS sRGB V2 profiles is in the presence of “unicode” tags. For example, here’s a tag from ArygyllCMS “sRGB.icm” profile (note the MacScript tag isn’t in all of ArgyllCMS profiles):
<ASCII><![CDATA[sRGB IEC61966-2.1 (Equivalent to www.srgb.com 1998 HP profile)]]></ASCII>
And here’s the equivalent tag from RT sRGB profile:
<ASCII><![CDATA[RT_sRGB gamma sRGB(IEC61966 equivalent)]]></ASCII>
<Unicode><![CDATA[RT_sRGB gamma sRGB(IEC61966 equivalent)]]></Unicode>
And from my own V2 sRGB profile (like RT’s profile and unlike ArgyllCMS profiles), there is the Unicode line:
So perhaps the printing place @cuniek uses somehow has V2 software in the pipeline, feeding stuff to the printer, that might stumble over the unicode parts of the RT profile?
But seriously this is just a guessing game as to what causes the Frontier printer to have issues with RT jpegs - what we really need is an example output jpeg from PhotoShop, that was output using the version and the specific color management settings that are used in the establishment with the Frontier printer.
If the Frontier printer only takes sRGB input, I’m curious why the processing pipeline even looks at any embedded ICC profile, as it could just assume the input is sRGB input. Though this would result in truly awful results for non-sRGB files sent to the lab. And if there really is a profile conversion going on from the embedded ICC profile to some other destination ICC profile, why doesn’t the Frontier printer fail on every single jpeg with the RT profile embedded?
Personally I don’t use V2 profiles when doing ICC profile conversions using LCMS or when image editing using LCMS as the CMM. Instead, I make profile conversions using the equivalent V4 profile. If I want a V2 profile in a final output file - such as uploading an sRGB image to the web - then I assign the equivalent V2 profile to the already converted image file, using exiftool, which I’m already using to add copyright and such, so it’s not really an extra step. But obviously my “workaround” is limited to standard matrix RGB output spaces.