On Saturday 05 August 2006 10:20, Frédéric wrote: > On Saturday 05 August 2006 18:33, Hal V. Engel wrote: > > I am not so sure that images in GIMP are "edited in sRGB colorspace". > > You are right: I forgot that Gimp let the user choose working colorspace... > But as you explain later, Gimp is not able to read embedded profiles. So > you have to choose the working colorspace, which much match the colorspace > of the image. Usually, sRGB, as most DSRL cameras output files in this > colorspace.
Some do some don't and some also let you select from several that are used by the built in camera image processing. sRGB and AdobeRGB are common. If you have this option and you are using in camera image processing then use AdobeRGB has it has about a 45% larger gamut than sRGB. When you process from RAW files using tools that are not from the camera vendor you will be getting images that are in the devices unique color space. This color space can be much larger than even AdobeRGB. My D70 for example when processed through UFRAW has a color space that is almost exactly the same size and shape as BetaRGB. BetaRGB has a gamut that is almost twice as large as sRGB (69% of Lab vs. 35% of Lab). So this gives you an idea of how much information is lost when one of these images is processed into an sRGB image. This is less of an issue with consumer level digicams since the much smaller sensor sites also have a much smaller gamut/dynamic range. > > I hope that the final 2.4 version will handle all the conversions between > colorspaces, the embedded profiles, and all problems it can produce when > loading image with different profiles... I agree. Like most open source software I think the issue is one of manpower. GIMP simply needs to have someone with the time and inclination to do this work. > > > > If you are not using Gimp-2.3, then, yes, I think your are right, and > > > you have to use the monitor profile as source profile. > > > > No this is not correct. You need to use whatever color space is correct > > for the image. If you captured the image with a camera or scanner then > > you need to use a profile for that camera/scanner to either work > > directly in that color space or to convert the image from that color > > space to some standard working color space of your choice such as > > AdobeRGB, ProPhotoRGB, BetaRGB.... > > But what to do when using an application which doesn't support profiles > (here, not using Gimp-2.3) ? Then, all corrections you are going to do > will bring your image in the monitor colorspace, because you will try to > have this image looking good on the monitor. Am I wrong ? This case is not > very clear to me... Do you want your images to end up in your monitors color space? I would try to avoid this and in fact would consider this to be very damaging to the image. There are a number of alternatives from using the GIMP development branch to using CinePaint that will allow you to avoid this. > > > If you do use a standard working color space avoid sRGB as it is simply > > too small to handle the gamut/dynamic range of most source material. > > This is particularly true for DSRL cameras where you process the raw > > data and for high dynamic range film scanners. Friends don't let > > friends use sRGB. > > Yes, it is true. And even when I don't use RAW files, my Canon 20D let me > output jpeg in AdobeRGB colorspace :o) AdobeRGB is way better than sRGB. For your typical DSLR you will maintain the gamut of about 96% of the image and only lose or change the color information of about 4% of the image. The loses are small enough that under most circumstances you will not notice. > > > I have been using CinePaint more lately. It has full CM awareness (it > > knows how to use embedded profiles for example) and will handle images > > with higher bit depths (16, 32 bits/channel as well as images with float > > and double values). GIMP is currently limited to 8 bits/channel. The > > disadvantage of CinePaint is that it's tool set is somewhat limited. > > But it does have all of the basic tools you need for most things and if > > your work flow consists of making basic image adjustments (color > > balance, contrast, brightness, curves, levels...) and cropping then it > > will do the job very nicely. > > When processing RAW files, all color corections are made in a linear space, > on the 12bits/channel. So, once the tiff/jepg file is produced, you only > need to use geometric tools in Gimp. It can be done without to much > damages, even in 8bits. By that time you the damage has already been done. I always process my RAW images down to 16 bit/channel output and I alway try to preserve as much of the information in the photo as possible. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
