Newbie CMYK question - alternate profiles?

Question

I am converting a whole series of images to CMYK for printing, in Photoshop CS3. All the originals are RGB 8 bit. I am surprised at the range of the results (as viewed on monitor) I am getting. It seems many images hardly change at all with conversion, some change moderately, and some are skewed a great deal. The moderate ones I am able to compose actions with adjustments that approximate the appearance under RGB. Some of the worse ones are so bad as to not be viable with any adjustments I have been able to make so far.
In particular, several of the files with large areas of blue sky are very badly affected - while others that also have large blue skies are almost completely unaffected and look great. The difference seems to be that those whose sky shade is closer to cyan display well, where those which are a saturated shade closer to true blue look terrible - dull and dark and lose all their luminosity, becoming a much darker shade of slate blue-grey. I also get contrasty bright halos surrounding trees in 2 cases.
Also, on a few,  large areas of saturated green foliage in the background seem to lose much of their yellow, causing the images to be much less zippy overall. Same thing with large red, orange, and lavendar areas, but this does not impact the image appearance as badly.
It doesn't make a lot of sense to me that the conversion would just pull so much yellow out of the saturated backgrounds (cmYk after all...), and leave the whites and other zones unaffected (so that if I just try to add the yellow back in, I lose the whites and other areas skew). Can this be minimized with any other settings or techniques?
Also: I have heard there may be numerous CMYK color profiles which can be applied as alternates when converting. How can I obtain and install these profiles? Will they alter the display characteristics with congruent press results?
Thanks for help with this!

Answer 1

David....a few last thoughts.  I assume you probably know this, but it is important and bears repeating.
The selection of your destination profile (whether press, inkjet, lightjet, digital press, etc) is important to good color.  Ideally, you want to use "an accurate, well-built, custom profile on a well calibrated device".  An accurate printer profile establishes the boundary of printable colors on the device, but it also contains large lookup tables that help you "re-map" colors from a different color space during conversion.  So, when you send jobs to a press, you would ideally like to have a custom press profile for the specific press, paper, etc.  That profile will normally only be accurate for that press and paper combination, and that assumes your commercial printer has a well calibrated, well maintained press, exercises excellent process control, and handles all the files properly.  There are a LOT of links in this chain. Many commercial printers do not actually profile their press...they profile their proofer instead, and supply "contract proofs" to their customers.  Once the customer signs off on the proof, it is then the printer's job to match their own proof on press (within tolerances usually specified by SWOP, which are fairly liberal).
You mentioned some of your images may be output on coated paper, and some on uncoated.  Coated and uncoated papers respond to ink differently, have different gamuts, different ink limits, etc, and would each require a different profile for optimum results. If you have selected your commercial printer, ask them for profiles for their press, or their proofer.  If they have neither, ask what they recommend, both for glossy coated and uncoated stock (or whatever you plan to print on). They may recommend an industry standard profile, such as US Web Coated SWOPv2, etc.  If they are their own profiles, ask for copies so you can convert to their standard for your given paper.
Then, use those profiles for conversion.  Images going to glossy coated stock should used the recommended glossly coated profile, and uncoated images use the uncoated profile.  You will undoubtedly see less color gamut on the uncoated paper, with more of a loss of color, at least on colorful originals.  You will probably want to convert each image individually, if you want the best possible output.  Bring up the Convert to Profile dialog, select the profile supplied or recommended by your printer, then try both Perceptual rendering, and Relative Colorimetric rendering to see which initially looks the best overall.  (use BPC with Relative colorimetric).  If you see a huge shift in color and dynamic range, it doesn't mean the profile is necessarily bad.  It probably indicates that your original has a lot of unprintable colors, at least on that press/paper combination. The rendering intents are different ways of cramming a larger gamut file into a smaller gamut space.  Editing the profile won't magically give you more colors, though it will redefine the tables for conversion and redistribute your colors differently.  That is not a recommended action unless you are very experienced and skilled at profile editing.
What you can do AFTER conversion is make some edits to your CMYK file (curves, levels, hue/saturation, selective color, etc) to try to get a little closer to the look and feel of your original.  You can never get it all back, because your original has unprintable colors, but you can often move in the right direction.  When you edit your CMYK file, you need to be careful to stay within the ink limits of the press/paper combination.  If you pump your file up too much, your job may be rejected by the printer.  So, if they specify a 280 total ink limit, and you pump it up after CMYK conversion to 320 TIL, expect your job to be rejected (or an extra charge to rework your job).
Rick McCleary's CMYK 2.0, or Real World Color Management can be very helpful in understanding all this.
And remember, well done images in print can look excellent.  But even images that look fantastic on the printed page in isolation can sometimes look a bit paltry when compared side by side with a super bright, colorful original RGB image on your monitor.  Welcome to the world of print.
Lou