Sorry for the nebulous reply but the answer to your first question is 'maybe'. Why are you going back and forth between cmyk and rgb? Usually, the best solution is to work the file in rgb and only convert it to cmyk upon output. You can also do this by embedding an rgb file as a smart object in a cmyk file.
You won't lose quality by doing this, per se, but by going from cmyk to rgb to cmyk could spell trouble if you are doing this for offset printing. The original cmyk file may have specific information for a certain press or black generation scenario. When you go to rgb and back to cmyk you are potentially destroying this black generation from the original and replacing it with something that may not print the way one wants it to.
Image started in CMYK and the filter I use you can only use in rgb
mode but I ned the filein cmyk for printing..digital. thanks for your
I'm curious to know your PS Color Settings. Bret is on the right track. However, I've been in the same position you are where I had a CMYK image and needed to run a filter in RGB. You should be OK if you maintain a defacto industry standard of CMYK = SWOP v2; RGB = Adobe RGB. Should you venture into other color spaces, then you may run into some conversion surprises. Getting back to my example, when I convert back to CMYK I see no human detectable shift. You could easily check this by running a series of tests using various profiles and writing down the percentages from the "Info" palette. In an event where you did experience a shift, you could adjust the CMYK "back" to where it was before using "Curves".
Yes that's what I was thinking re curves.
I've had to synch my apps with the publishers recommendations
(Blurb_ICC_Proflie.icc and also using export:Blurb PDF X-3 Export
Preset v1-1) as follows, though I don't understand what it means in
ID's "Preserving the numbers and ignore linked profiles" ...what
Pug, you're totally on the right track. Bring your image into your preferred RGB color space (Adobe 1998 is best suited for printing. I'm also assuming your monitor is calibrated), do your work and save. If you're using InDesign you can place the RGB image in your document. When you use the Blurb job options to export a PDF, the PDF engine will automatically convert your RGB image to the proper (Blurb) cmyk color space for digital printing.