Colour separation - jpeg files

[polly1]

is it possible to colour separate jpegs for print in photoshop???

[Hippy]

Image - Mode - CMYK will do this for you. To see the separation layers activate the channels pallete. Window - Channels will do this. This pallete allows you to switch the colour seaparation layers on and off.

[polly1]

Thanks! after i have done this should a printers be able to use them. They are threatening to litho print the whole thing for a cost?

[Hippy]

You produce the separation layers as separate images by selecting the mode. If you then save-as and choose a name "bla-blah.jpg" or better select the format to TIFF and name it "blah-blah.tif" you will save it in the CYMK mode and that is how it will open. The TIFF type will not compress your image and produce artefacts like a JPEG compression can. Printers (the people who do the printing) prefer that format as well.

[Hippy]

Thinking about your core problem. The printer person wants to produce plates for the cyan, magenta, yellow and black printing. Merely switching mode in Photoshop may not produce the best results as there will some "out of gamut" colours. That is some colours in the original RGB image will not exist in the CMYK process.

Without loads of tryouts on the actual printing process you will not be able to match the colour gamut and produce a passable final result. Why not let the printer person do this for you. After all, his expertese will be far more than you will ever be able to produce in Photoshop in an amateur sort of way.

There is an extensive section in the Help section of Photoshop on how to produce CMYK separation prints for litho process. I am sure it not just switching modes like I suggested at first. One of the major drawbacks is that you are looking at coloured light mixing on your monitor, and a printed page gives you reflected light. One add the colours and the other subtracts them. What looks good on the screen may look awful when printed. For the home printer machines you can use preset colour profile modifiers to change things at the printer to try and match the screen.

It will be almost impossible to match YOUR screen with HIS printing process.

[polly1]

Thanks v. much Hippy. i will look in the help bit. I changed the mode to CMYK but i know i should have started like that from scratch. i have never known a printers to ask for this - i usually just send the jpegs and stuff, my lack of knowledge i suppose. Anyway your help was much appreciated!