Color Proofing Tips

Color specified in Photoshop is spoiled on a large, expensive proof! Hold on! Use these tips first!

David in Louisiana on a Dell running Photoshop 6.0 writes

I have created a very large image for a client of mine. Ive never really had to work on a picture this big. 50 inches in height, and 70 inches in length.

My problem is when I print out a sample to show my clients the blue in the background prints in purple. At first I thought my ink cartrige was just running out and thats why. Well I took it to kinkos to have the large image printed out and it prints in purple there to. The guy there said something about how the computer compiled it and stuff like that. I dont know what that means and more importantly how to fix it! He also told me to look at how the color was set up. I believe its in RBG. He said try it in Pantone. What is your take on the situation. Does this happen on Large images. Im not an expert on Photoshop as you can tell. But, I am getting paid for this job. I need help STAT! Can someone tell me what I need to do? Thanks for listening to me whine.

Big Job

First, you didn't say, but I'm assuming the job is going for process color litho printing. At 50 x 70 there's bound to be some moo-lah in the budget for proofing. It's a big job, and a real shame to spoil one of those prints.

There are many different variables that can affect color we really can't cover them all in this single post. The most important rule here though is to understand the type of equipment which will be doing the printing. If it requires CMYK, then that's the color space you need. RGB almost always presents bad results printing to a CMYK printing device. So ask the vendor first. If you're proofing or 'sampling' on a different machine than will be doing the actual color output, that's another pitfall -- you'll need two versions of the file -- one for each output device.

Screen color is almost never reliable for color matches -- particularly in the blues to purple ranges. (The monitor itself introduces blue into the color thus making the printed image more "purple") We always stress never proofing color on a monitor when the color results are critical, or when it's a high-dollar job. We'd certainly rather put out a few bucks to get the color right first -- rather than eating a huge print later.

Do you have a PMS specifications guide? If so look up the PMS number and BUILD it using the "Custom Color" palette, and CMYK values. If you have the PMS color set installed you should be able to make a 'reasonable' selection from that.

Click the foreground color swatch in the Tools Palette
Click "Custom"
Click and hold the "Book" pop-up and you'll be presented with a number of pre-installed color models. Select the Pantone selection which reflects the paper you'll be printing on. If this is to be printed on vinyl, acrylic or other nonporous surface, then select "Coated" -- but beware: proofing to plain bond or other absorbent media will produce decidedly different color than the final.

If you do not have the Pantone PMS specifier, let us know what color you're looking for and we'll give you the recipe.

The FILE needs to be converted to CMYK for litho printing anyway. Kinko's should give faithful reproduction at that point -- chances are, your Inkjet color printer won't.

ALWAYS TEST on a small sheet:

Build your color chips -- an array of "Blues" that would "seem" close and run a TEST page. (Match your proofing paper as closely to the final stock as possible.)

After the results of that, rebuild your background. (I do this all the time for large projects -- even before the first proofing go-around.)

BEWARE: once the job goes to the color litho printer, the colors will potentially change again. You should be working with the ultimate litho printer rather than Kinko's. A 50 x 70 printing job ain't no small job. They'll have a "proofing" printer that gives 100% or near 100% color, and you should adjust to that.

It's really the only way to be "sure" -- the last thing you need is to have the client sign off on a color sample then have the litho job color shift south!

We've seen it happen -- and seen skids of printed paper go to the landfill. Not a pretty sight.

Please keep us informed of progress.

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http://www.graphic-design.com/Photoshop/Tips/index.html
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http://www.photoshop911.com/emergency.html

Comments

[Full Color Printing]

I actually was faced with this problem some time and did not find the solution to it

[S D]

I want to know how to proof a PMS color, the low tech way.

[CJ]

I have changed a file from RGB to CMYK for printing on business cards. The flesh tones on my subjects are red. How do I adjust this in photoshop?

[Nickelkitten75]

Printing an 50x70" image and an 8x11" print data doesn't really matter. The color shift that your talking about is largely due to the discrepancies caused by the CIE L*a*b* color space model. You see when data gets to be printed on an inkjet printer there's what we call gamut mapping from the Monitor to printer color gamuts. One of these descripancies that the Lab color space is that it greatly exaggerates yellow and oftentimes underestimates blues. The hue in the blue quadrants is basically overpowered by the energy brought by the purple stimuli. So printer manufacturers really have to compensate this imperfection in the Lab color space and do extrapolation instead in their driver algorithm to get the exact gamut mapping of the nearest blue neighboor.

I hope this will answer your queries...Let me know what you think otherwise.

*Nickel...