RGB to CMYK Conversions

[terbyr]

My first photo book is also my publisher's first one, and I feel like I've wandered into an Alice in Wonderland world trying to deal with the printer. They seem not to have any idea what I'm talking about when I ask for an ICC profile, but they patiently send tons of completely irrelevant info. The designer, in the meantime, tells me not to worry because we can correct the proofs. The publisher, who's used to black ink only, is lost.

Sorry for the wordy intro because I do have a simple question. When I convert my RGB files in PhotoShop to CMYK (conversion to a generic swop coated), I note that the histogram changes considerably. The blacks suddenly get weak. If I adjust them in levels, it looks too dark onscreen.

Should I ignore the onscreen appearance and move the slider so I've got the full 0-255 range or should I get it looking right in RGB, convert to CMYK, and ignore the weak blacks?

Final deadline is about to land on me. Help much appreciated.

Terry

[Kirk Gittings]

In all honesty the amount of inexperience evident here with the printer/publisher and you not having done conversions before would scare the crap out of me. Read this it helped me allot:

Jeff Schewe CMYK Conversions

[Scott Martin]

I would suggest downloading the latest greatest SWOP (grade 3) profile from:

http://www.gracol.org/resources/iccdownload.asp

and convert your images to this newer SWOP profile using "Convert to Profile" with Relative Colorimetric and Black Point Compensation. These newer profiles offer better conversations to CMYK than Adobe's somewhat outdated profiles.

Aside from that I would place greater confidence on SWOP certifiable hard proofs than what you are seeing on screen. I'd encourage you to keep your RGB range within 7-249 instead of the full 0-255 to avoid blown out highlights and shadows.

There is much, much more to discuss but there are some good, simple guidelines that should be pretty easy to move forward with.

[terbyr]

In all honesty the amount of inexperience evident here with the printer/publisher and you not having done conversions before would scare the crap out of me. Read this it helped me allot:

Jeff Schewe CMYK Conversions
[a href=\"index.php?act=findpost&pid=222886\"][{POST_SNAPBACK}][/a]

You're absolutely right.

I really appreciate the link to the Schewe piece. It taught me a few things about output sharpening that I didn't know. The difference in the RGB and CYMK histograms and the uncertainty about whether to stretch out the CMYK conversion for the full (or almost the full) dynamic range is still a mystery, though.

In any event, many thanks.

Terry

[terbyr]

I would suggest downloading the latest greatest SWOP (grade 3) profile from:

http://www.gracol.org/resources/iccdownload.asp

and convert your images to this newer SWOP profile using "Convert to Profile" with Relative Colorimetric and Black Point Compensation. These newer profiles offer better conversations to CMYK than Adobe's somewhat outdated profiles.

Aside from that I would place greater confidence on SWOP certifiable hard proofs than what you are seeing on screen. I'd encourage you to keep your RGB range within 7-249 instead of the full 0-255 to avoid blown out highlights and shadows.

There is much, much more to discuss but there are some good, simple guidelines that should be pretty easy to move forward with.
[a href=\"index.php?act=findpost&pid=222889\"][{POST_SNAPBACK}][/a]

I'm amazed at how much better these SWOP profiles express the dynamic range of the original file. And I appreciate the 7-249 reminder. (I thought this was the case but, once again, the printer played dumb.)

One further question, though. Do you know offhand the difference between the SWOP2006_Coated3v2 and the SWOP2006_Coated5v2? I used the second because it looks like a newer version.

Mnay thanks.

Terry

[Scott Martin]

One further question, though. Do you know offhand the difference between the SWOP2006_Coated3v2 and the SWOP2006_Coated5v2[a href=\"index.php?act=findpost&pid=222908\"][{POST_SNAPBACK}][/a]

"Coated3" is for coated grade 3 press stock and "Coated5" is for lesser quality coated grade 5 stock. GRACoL is the specification for grade 1 premium stock. When people generically say "SWOP" they refers to SWOP grade 3. When people are working with awful grade 5 paper they are usually better about saying "SWOP5" because of the assumption otherwise for SWOP3. Does that makes sense? Use SWOP Coated3 unless you have reason to do otherwise.

Again, there is lots more to talk about but that's the best profile for common use at this time unless you have good information that another profile or press specification would be better.

[terbyr]

Does that makes sense? Use SWOP Coated3 unless you have reason to do otherwise.
[a href=\"index.php?act=findpost&pid=222913\"][{POST_SNAPBACK}][/a]

Perfect sense.

I couldn't appreciate the help more.

[Kirk Gittings]

I would suggest downloading the latest greatest SWOP (grade 3) profile from:

http://www.gracol.org/resources/iccdownload.asp

and convert your images to this newer SWOP profile using "Convert to Profile" with Relative Colorimetric and Black Point Compensation. These newer profiles offer better conversations to CMYK than Adobe's somewhat outdated profiles.

Aside from that I would place greater confidence on SWOP certifiable hard proofs than what you are seeing on screen. I'd encourage you to keep your RGB range within 7-249 instead of the full 0-255 to avoid blown out highlights and shadows.

There is much, much more to discuss but there are some good, simple guidelines that should be pretty easy to move forward with.
[a href=\"index.php?act=findpost&pid=222889\"][{POST_SNAPBACK}][/a]

Scott a clarification please......you are not suggesting this SWOP (grade 3) instead of using a custom printer profile when it is available right?

[Scott Martin]

Scott a clarification please......you are not suggesting this SWOP (grade 3) instead of using a custom printer profile when it is available right?[a href=\"index.php?act=findpost&pid=222922\"][{POST_SNAPBACK}][/a]

A custom *press* profile? Custom press profiles can be wrought with problems but if you decide to work with someone that recommends you use their profile, then, yes, by all means use that. But generally speaking (and I do mean generally) the latest IDEAlliance SWOP profile is the best choice we have today when working with print shops that are (or should be) calibrated to SWOP.