Waiting for the next scheduled release will be ok for Rawtherapee as it is no problem in normal use. I discovered this issue when doing HDR testing which is more of a future thing and not a main thing RT does today.
I have not tested Photoshop, but as they have supported floating point tiff and HDR for a while and usually embed an icc profile in those I would guess they do floating point interpolation (i e curve fitting or linear interpolation) of the gamma curves at least, not sure how possible it is to make interpolation of the LUTs. In the HDR case it's generally more important to avoid banding (i e clamping pixel values to a 16 bit linear space) than having high precision in the color transform. Floating point tiff has been a bit outside any official specs but has become a de facto standard in HDR and one of the few HDR formats that provide some sort of color management. The default lcms2 version for RT is currently 2.2 so I guess the nocache option needs to be kept for a while. /Anders On 12/08/2012 06:03:45 PM, Marti Maria wrote: > > Hi, > > Cool, with this patch more "normal" profiles are promoted to the > unbounded mode. > > Just one comment, please note the unbounded mode is a feature > of lcms2 and it is implemented only by lcms2 so it is NOT supported > by other CMMs. For example, with Photoshop you are likely to > obtain the quantization to 16 bits, which is maximum the precision > ICC profiles using Lut16 or LutAToB would have, following ICC spec. > > In this way, this was not really a bug but a lack of support for a > certain lcms2 extension. Anyway, I think your patch is great > because adds more types to the pool of profiles supporting > unbounded mode. And it does by just slightly changing > one stage implementation. Excelent! > > But since this is not a feature expected in a 16 bit ICC workflow, > I guess it could wait to the next release. I usually do releases > each 6 months. Please let me know if this is ok to you. If the > impact for rawtherapee users is severe, I could study an emergence > release. But I would like to reserve this for vulnerability issues > only. > > I have committed your changes to GIT. Thanks again for providing the > patch. > > BTW, I've seen in the comments something like > > " cmsFLAGS_NOCACHE ); // NOCACHE is for thread safety," > > This is no longer required. Each call to cmsDoTransform() keeps its > own > cache copy, so from 2.3, cache is thread safe. I do extensive use of > this on > my applications and it works fine in >10 threads running > simultaneously. > > Best regards > Marti > > El 08/12/2012 15:30, Anders Torger escribió: > > There seems to be a special case with linear gamma icc profiles > which > > causes tonecurves to become 16 bit tables even for floating point > math > > which leads to precision loss. In normal applications this is not > > detected as it is buried in deep shadows, but in HDR it is. > > > > To me this seems to be a bug. > > > > More detailed analysis can be found in this issue report for > > rawtherapee (which uses lcms2), which also includes a suggested bug > > fix by patching cmstypes.c: > > > > http://code.google.com/p/rawtherapee/issues/detail?id=1642 > > > > (lots of discussion, read the last comments and up to get to the > point > > immediately). > > > > If there is a workaround that does not require patching lcms2 > please > > let me know. > > > > /Anders > > > ------------------------------------------------------------------------------ > > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial > > Remotely access PCs and mobile devices and provide instant support > > Improve your efficiency, and focus on delivering more value-add > services > > Discover what IT Professionals Know. Rescue delivers > > http://p.sf.net/sfu/logmein_12329d2d > > _______________________________________________ > > Lcms-user mailing list > > Lcms-user@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/lcms-user > > > > ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
