Re: Profile to Profile
Re: Profile to Profile
- Subject: Re: Profile to Profile
- From: email@hidden
- Date: Fri, 12 Oct 2001 19:57:50 +1000
>
lets say i have a customer CMYK file with an embeded profile and they
supplied a proof that they want me to match on my proofing device.<
John, what are results like if you simply pass through the existing CMYK colour values without converting the numbers? How different are your conditions to those of the clients separation?
>
so i
convert to my profile and everything looks great except the black only
shadow that existed in the original file is now a cmy shadow.<
Unless the file was separated using max gcr or perhaps heavy in some cases - this would be a human generated shadow, not one from a separation algorithm. UCR, and GCR lt/md should produce CMY and CMYK shadows depending on the original luminosity of the
shadow.
>
should i be
converting to my custom CMYK ?<
That depends. If attempting to match a proof of some description, does the embedded profile actually describe the proofing method - or a more general method such as SWOP? By using the tag in the conversion, you may or may not be describing the actual proof
colours. Who knows?
I guess there are three options: (a) dont convert and see how the file proofs with your system (b) use the tag and convert (c) assign a differnt tag which makes a better conversion to your preferred output profile.
If you are attempting to see what the supplied sep looks like in your proofing conditions, with press output the goal - then you would probably _not_ convert and pass the numbers through unchanged.
Usually if a file is pre separated to CMYK - there is a good reason for choosing that method.
The files originator probably does not want this image repurposed (converted) - due to the very things you mention (custom separation info lost). A tagged RGB or LAB file should probably be supplied if the user wants the data converted.
If this is not the case, and everyone is happy with CMYK > CMYK conversions - then the new black generation will be dependent on the destination profile (unless the CFM plug mentioned by Alexey Gribunin is used [sounds excellent]).
>
whats the correct way to
handle this ?if i dont convert the proofs look green.any suggestions ?<
The proofs look green on the softproof, or the actual hard copy proof?
If the output - then there sounds like a major problem somewhere...
If the original shadow is K only (neutral) - and the sep prints greenish - then it _must_ have higher ratios of cyan/yellow than magenta and/or black. If all were equal at 100% CMY - one would expect a warmish, dirty brown 'black'.
Does the destination profile usually produce neutral prints for CMY greys?
In Photoshop - run the cursor over the shadow and ispect with LAB values in the info palette. If the AB channels are both 0 or one or two points either way - then this shadow should print neutral (if the current CMYK profile is correct).
If everything in the profile/conversion/files check out - then it may be a hardware or printing inks/substrate issue.
Hope this helps,
Stephen Marsh.