Rgb to cymk

[Richard_a_Ward@adobeforums.com]

I have some photographs that a magazine wants in cymk. The originals are 8 bit RGB. Someone suggested that I convert to 16 bit rgb before I convert to cymk. After the cymk conversion back to 8 bit. Is there any other suggestions about converting to cymk ??

thanks

[Ramón_G_Castañeda@adobeforums.com]

You won't gain anything by converting from 8 bit to 16 bit. If the information/range/details aren't there in 8-bit mode, converting to 16 bit won't magically create them.

[Richard_a_Ward@adobeforums.com]

That's what I thought. The person giving the advice must have thought that I was starting with a 16 bit rgb original. That would make sense.

Other than that bit of nonsense. Do I need to adjust for out-of- gamut colors are just go by what looks best on my calibrated monitor.

Thanks

[Peter_Figen@adobeforums.com]

If he had suggested that you convert to 16 bit he must have at least asssumed you had an 8 bit image. It doesn't really matter. In all but the most extreme cases, you'll see no difference at all converting to CMYK. Generally speaking, you don't need to make adjustments for out of gamut colors. If you've got colors that are mildly to moderately out of gamut, use Relative Colorimetric and let the colors fall where they may. In extreme cases, Perceptual sometimes gives a better conversion. No matter what rendering intent you use, it's always a good idea to check the info palette for contaminated colors and ink densities, using Selective Color to make final tweaks before press.

[Neil_Keller@adobeforums.com]

But, of course, the underlying problem is that the CMYK ink gamut is noticeably smaller than RGB light. Colors such as clean bright orange, green, or purple will suffer heavily. On the otherhand, when looking at pages of well-crafted CMYK print reproduction, no one seems to notice that.

Neil

[Mike_Ornellas@adobeforums.com]

It really kind of depends on what you are speaking about when converting an 8 bit file into 16 bit for better image quality.

In general, it's a waste of time, but trying to correct difficult vignettes and masking, etc, 16 bit is the place to be even with standing 8 bit files with existing problems. The creation of 16 bit vignettes from scratch is hugely superior from 8 bit.

bits, bite!

[Andrew_Rodney@adobeforums.com]

The Adobe ACE CMM is a 20 bit algorithm.

[Tim_Lookingbill@adobeforums.com]

Andrew,

I've been seeing this 20 bit claim pop up in Adobe Forums. Can you direct me to info on what this means?

Thanks

[Andrew_Rodney@adobeforums.com]

This was discussed awhile back on the Apple Colorsync list by Chris Cox. You can search the archives but I suspect Chris will chime in well before you can find the posts (the search on this list isn't all that wonderful). But in a nutshell, the Adobe ACE is using 20 bit precision to in doing the calculations and as far as I know, the other available CMMs are not.

[Tim_Lookingbill@adobeforums.com]

I guess it creates smoother transitions. Is there an Apple Colorsync list on Adobe's site?

I guess I'll go lookin'.

Thanks, Andrew.

[Andrew_Rodney@adobeforums.com]

-->Is there an Apple Colorsync list on Adobe's site?

Go here:

[email]colorsync-info@public.lists.apple.com[/email]