Scanned/processed/printed color matching

MV
Posted By
Michael_V_McCallum
May 7, 2004
Views
496
Replies
15
Status
Closed
We scan a printed book cover in RGB because that is the scanner format. Now we color match with a pantone book, spend alot of time in PS working with it, and convert to CMYK because that is the printers format. Of course we have some colors that can’t be made from RGB. The monitors make it impossible, since there is no way to profile correctly. Then the ink bleed of the original comes into play and everything gets worse. Is there a better way?

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RW
Rene_Walling
May 7, 2004
Colour management?
L
LenHewitt
May 7, 2004
Michael,

Now we color match with a pantone book, spend alot of time in PS working
with it, and convert to CMYK <<

Convert to CMYK first, but make sure it is THE SAME cmyk that the output device uses. That means selecting a CMYK working space that matches the output device.

The monitors make it impossible, since there is no way to profile
correctly.<<

Adobe Gamma will produce a perfectly acceptable calibration on CRT monitors. If you have LCD monitors you will need to purchase 3rd. party calibration tools.
GH
Gary_Hummell
May 7, 2004
An excellent reference is:
Real World Color Management by Bruce Fraser, Chris Murphy, Fred Bunting

Gary
MM
Mac_McDougald
May 7, 2004
I have yet to find a full CMYK swatch book.

AFAIK, doesn’t exist.
Even though CMYK can’t duplicate certain RGB colors, there are still 16.7 million theoretical possibilities at 8bit depth.

You wouldn’t be able to lift the book, even if the swatches were only 1" square!

Mac
MV
Michael_V_McCallum
May 7, 2004
Yeah, I know all about the color management. That’s not the issue. What I get from the scanner is way too lengthy to color match in the pantone book. Plus then you get those shades that don’t exist in pantone, but may in CMYK, or may not. I have yet to find a full CMYK swatch book. Yes, I gotta do it quickly, but it has to be right!
Thanks for the help!!!
MV
Michael_V_McCallum
May 7, 2004
I have not found Adobe Gamma to be anywhere near close to reality on my CRT monitor. Could be I am missing something.
CC
Chris_Cox
May 8, 2004
Adobe Gamma should calibrate and characterize CRTs without any problems. Unfortuantely it doesn’t work for most LCDs.

Yes, you might be missing something.
GH
Gary_Hummell
May 8, 2004
Michael, you might try dividing your post up into specific single questions with as much detail as possible. There are some very knowledgable people contributing to this forum but background details help. I believe you are basically asking at least 6 questions above. Just a suggestion.

Gary
MV
Michael V McCallum
May 8, 2004
Thanks Gary,
Here goes…
What I really need to know is how to be sure each color on the original cover is reproduced as closely as possible when the commercial book printer prints it in CMYK. Because of the scanner color shift, the "Eyedropper" tool gives me a bad color. I have been using the pantone book, but am hoping there is a better way
mike
GH
Gary_Hummell
May 8, 2004
If your scanner doesn’t have a good import profile, you can scan the book cover simultaneously with a grayscale wedge (Kodak provides them). By using curves in Photoshop to adjust the 20 step wedge to neutral, you should be very close to correct numbers for your cover. It is more intuitive to work with curves like this in RGB and then convert to CMYK, IMO. There may be a more clever way, but this works for me.

Gary
DM
Don_McCahill
May 8, 2004
I would not use the Pantone book in a RGB to CMYK conversion. It is designed solely for specifying spot colors, not CMYK ones. A lot of Pantone colors cannot be duplicated in CMYK.
MV
Michael V McCallum
May 10, 2004
Gary, thanks but a 8 covers an evening (i have another job), that could be a killer on time. Has you guys tried the spectrometer solution? Or is that unrealistically expensive?
GH
Gary_Hummell
May 10, 2004
Actually if your scanner can be set to a manual mode, the curve you work out for the first cover could be saved and reused for subsequent covers. In that sense you are characterizing the output of the scanner at those scanner settings. The important thing is to be sure the scanner is not doing automatic corrections each time. Of course you still have the limitation that there are many specialty inks and surface treatments that are used on book covers that simply aren’t scannable. Some would be better captured with a camera.

Yes, a spectrophotometer would be useful but expensive.

Gary
MV
Michael V McCallum
May 14, 2004
Gary, Just bought one of the pantone handheld spectrometers for about $300. So far it is right on. Maybe it will be the solution. I will post again when I have more experience with it.
Mike
MV
Michael V McCallum
May 19, 2004
Report on the Pantone Spectrometer- Results so far are very accurate. The only problem so far is the size of the sample. It seems to need an area a little smaller than a dime to scan correctly. But then again for cheap money I shouldn’t ecpect too much. Overall I am pleased with the item and it speeds my work.
Mike

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