Thread: Re: [Lcms-user] profile conversions?
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From: Richard R. <rs...@ea...> - 2003-09-18 21:25:36
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Thanks for the responses. I see the problem now with working in the scanner color space. I actually have access to a nice drum scanner which is self-calibrating and whose color space is actually a well defined wide gamut RGB, but my home flatbed is far from that. I was just reading a lot about various wider gamut spaces and Bruce Lindblooms BetaRGB looks like a good candidate in that its primaries are closer to those of both of my scanners than AdobeRGB is. Cheers, Richard -----Original Message----- From: Gerhard Fuernkranz <nos...@gm...> Sent: Sep 18, 2003 11:27 AM To: "Richard S. Ross" <rs...@ea...> Cc: lcm...@li... Subject: Re: [Lcms-user] profile conversions? Richard S. Ross schrieb: > My current workflow involves working with scanned files to which I > only 'assign' my lcms generated profiles in Photoshop. That is I use > the scanner profile as the working space and only perform an actual > conversion to a printer profile when I actually print. My thinking was > always, the fewer conversions the better. Is this correct or is more > damage being done by editing in the larger gamut scanner color space > than by performing multiple conversions? Monitor previewing always > involves conversion from your working space to the monitor profile, as > I understand it, so what advantages/disadvantages are there in using > another an additional profile/space in the process? Hi Richard, IMO it depends on wheter you also want to perform image processing operations in Photoshop. Many operations make assumtions, which are only fulfilled in typical working spaces like AdobeRGB or sRGB, but which are _not_ necessarily fulfilled in the scanner's RGB color space, e.g. R=G=B for all neutral colors. For instance, applying the same gamma to all three channels will keep neutral colors neutral in AdobeRGB or sRGB, etc., but it may change the chomaticity of neutral colors, if applied directly to RGB values in the scanner's color space. Therefore usually a working color space with well-defined properties is used to carry out the image manipulations. If you worry about accuracy, I recommend to use 16bpp for intermediate images and a wide-gamut working color space. Regards, Gerhard ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Lcms-user mailing list Lcm...@li... https://lists.sourceforge.net/lists/listinfo/lcms-user |
From: Roger B. <gr...@vi...> - 2003-09-19 19:43:15
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> Thanks for the responses. I see the problem now with working in the > scanner color space. I actually have access to a nice drum scanner which > is self-calibrating and whose color space is actually a well defined wide > gamut RGB, but my home flatbed is far from that. I was just reading > a lot about various wider gamut spaces and Bruce Lindblooms BetaRGB looks > like a good candidate in that its primaries are closer to those of both of my > scanners than AdobeRGB is. > > Cheers, Richard Personally, I want to find some time to start in the habit of using Bruce Lindbloom's excellent BetaRGB color space. I think it's a better idea than AdobeRGB but AdobeRGB has the advantage of being widespread -- it's on all Photoshop's recent installations -- as opposed to BetaRGB. I know BetaRGB is only a download away but, to make things easy for the average, non-ColorSync saavy user, AdobeRGB is more than enough. I've always wonder whether it made any sense to keep a scan in the original scanner color space since the intent is always to move it forward. For editing, I could consider leaving the image in the scanner space but soft proofing in either AdobeRGB or US WebCoated SWOP v2, if I am going to go to press with my images. Mind you, in practice, I never bother to kick soft proofing in and go straight for editing in RGB. Especially with my recent acquisition: a Nikon D100. I shoot in sRGB and when I open up my images in Photoshop, I make my color corrections right from sRGB. And leave my images in sRGB into my InDesign layout right through the printer! Just picked up a calendar I designed for a client today, at a local offset print shop, and, men, am I satisfied with the colors! I am a little lazy and wreckless these days... Regards, Roger Breton | Laval, Canada | gr...@vi... http://pages.infinit.net/graxx |
From: Jeff H. <jh...@co...> - 2003-09-19 19:43:48
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My understanding also is that workspace profiles such as Adobe RGB are perceptually uniform, in the sense that edits of the same increments anywhere amount to the same amount of change. I can't explain this with color science, but I have heard it (as well as the point already made about neutrality) in discussions of abstract workspaces vs. device spaces several times. -- Jeff |
From: Gerhard F. <nos...@gm...> - 2003-09-20 08:45:15
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Jeff Harmon schrieb: > My understanding also is that workspace profiles such as Adobe RGB are > perceptually uniform, in the sense that edits of the same increments > anywhere amount to the same amount of change. No, not really. But of course more uniform than for instance a raw scan with gamma=1. I cannot imagine that a preceptually uniform RGB color space, based on additive mixing of three colorants, is realizable at all, is it? Perceptually uniform color spaces like the CIECAM02 or CIECAM97s appearance models, or CIELAB (only approximately uniform) are on the other hand usually based on a lightness/hue/chroma representation of the colors, so image manipulation algorithms designed for a trichromatic RGB representation cannot be applied to colors in these color spaces (e.g. in Photoshop you can use a CIELAB working space if you want an approximately perceptually uniform working space, but then you will notice, that many operations are either not available or behave differently than in RGB). Regards, Gerhard |