Any thoughts on using Photoshop as a Proofing RIP??? Is this possible???

Discussion in 'Other RIPs' started by discountprintingservice, Jan 26, 2012.

  1. discountprintingservice

    discountprintingservice Senior Member

    Mar 2007
    I have been studying up for a while now on color management, rip software for proofing and finger printing presses for dot gain and gray balance.

    While brainstorming I came up with an idea to use Photoshop to function as a RIP for contract quality proofs. Here is my thoughts and I would like constructive input.

    First I have calibrated my press for dot gain & gray balance using a press room densitometer and my CTP RIP software.

    Next I take a composite PDF test file and open it in Photoshop at 300 dpi CMYK. This test file has the same patches used on press for measuring % values of c, m, y and k from 0% to 100% as well as grey balance patches. I print this file using the Print with Preview box, setting the screen frequency and dot shape (even thought the printer won't print dots it replicates as stochastic tones). I print a test file using contract proofing paper on my Epson Stylus Pro 7600 with Ultrachrome inks.

    Then I measure & record all the patches for dot gain of c, m, y and k, and the values for the gray patches (i.e. Cyan 60%, Magenta 60%, Yellow 60%) using our PRESS ROOM DENSITOMETER.

    WHY? Because in theory the proof should be calibrated to match the press sheet, so I want to use our press room densitometer readings from the proof to create transfer curves to simulate on the Epson what the offset press prints, rather than profile the proof with a spectrophotometer and create a icc profile (which by the way doesn't work well).

    I then create a transfer curve in Photoshop for each color independently using the recorded values and then proof the target file again to verify the reading & curves are correct.

    I save this transfer curve checking the box for "Override printers default function" under the transfer button, under print with preview. This tells the printer to use the Photoshop transfer curves instead of the default RGB curves in the Epson printer driver. This curve will be applied to all printed proofs from here forward.

    Note: For 2 color proofs I open a composite file, and use the channels palette to print only 2 of the 4 process colors (i.e. cyan/magenta or yellow/black). This gives me a 2 color proof and a 4 color proof for our 2 color press.

    In theory this should set Photoshop up to emulate what expensive RIP software will do. And with Photoshop's color management settings and using your calibrated monitor and/or printer profiles this should provide you with a very accurate proof that should closely match the gamut of your finger printed offset press.

    I am testing this theory this week, but would love input from anyone with extensive knowledge on this subject.

    This should work with or without the use of GCR or UCR.
  2. IgenSkeptic

    IgenSkeptic Member

    Apr 2012