Sunday Mailbag

March 28th, 2010 | Posted in General

Q: I’m just wondering if there are any special consideration you need to take in your illustrations, colour wise, that you know are going to be printed?¬¨‚Ć I know in animation, when a background is being painted in Photoshop, there’s a filter that checks if the colours will show up on TV, but is there similar issues with colouring for print?

A: There are a few things you need to keep in mind about colors in print, especially when it comes to digitally created art.

First off, and probably the most immediate concern, is the difference between the colors you see on the screen and that which ends up in print. It’s difficult to get the two to come close to being a match, because the nature of the two images, computer screen and printed page, as so different.

The image on your screen is produced using three colors, red, green and blue (RGB) at a resolution of usually 72 dots per inch. However because the computer screen displays these using an ADDITIVE color system (meaning a 0% of all colors equals black)  and as a transilluminated image (the colored light shines out from the screen) an image on the computer can display millions of colors with  much greater range of contrast and intensity as well as a broader and more subtle range of color (color gamut).

A printed page image, using a standard four-color process, is printed using four colored inks: cyan, magenta, yellow and black. Printing uses a SUBTRACTIVE color system (meaning a 0% of all colors equals no color or the blank paper) and relies on light reflected from the surface of the page as opposed to light from within. This limits the printed page’s colors, contrast and intensity. All this leads to a difference between what you see on the screen and what gets printed on the page.

With a good monitor and a color calibration system you can get some decent results with color matching, but since different magazines use different paper stocks, different ink densities and other factors, color will never be across the board consistent. Also the greater color gamut of a computer monitor can show you colors on the screen you cannot ever replicate in CMYK print. Personally I use the eyeball method. I take printed versions of my illustrations and hold them up to the monitor, then adjust the color balance to get as close as I can to the printed version. I have found I can get close that way, especially if I choose to match a certain range of colors more than others, and then whatever the differences between client’s printing end up negligible. I have found that by matching up the fleshtones in my images I get good results… as long as I keep in mind that the blues in my image need to be more subdued as they will print darker and more intense than the screen shows. When doing work I know will be printed on newsprint or a similar spongy stock I purposefully paint more garishly with the color knowing it will be muted due to the soaking in of the ink on the paper. I do this when I do newspaper illustrations or work for one of the Scholastic magazines.

I also always color my images as CMYK images in PhotoShop, as opposed to coloring them as RGB and then converting them. It doesn’t seem like it but the screen color does change when you do that conversion and it will be different than if you made the color choices in a CMYK mode in the first place. Also, PhotoShop will show you a little exclamation point symbol in the color palette if you have selected a color that is impossible to reproduce in print and will suggest the closest match to it that is reproducible.

One thing to keep in mind is the ink density of the target printing process. Ink density refers to the percentage of coverage of the four different inks on the paper of a given magazine or publication. Printers use a scale of 0% to 400%, 0% being on ink and 400% being 100% ink coverage of all four colors. What the ink density is depends a lot on the type of paper and the quality of the printing… glossy and heavier stock can handle a higher ink density than thinner or more porous paper. No matter what the type of paper, no one can use 400% ink density… the ink would literally never dry on the page as it could be too thick and gooey. A high quality, glossy magazine might allow an ink density of 300% or a tad more… this results in very rich blacks and a good contrast image. A less expensive printing process might have a max ink density of 270-280%, which leaves a bit to be desired in the contrast and black areas.

PhotoShop already knows this, and the color profile of a given image can have the ink density capped at any level one might desire. The default PhotoShop CMYK profile, U.S. Web Coated (SWOP) v2, caps the ink density at 300%. If you select what seems like “total” black from the PhotoShop swatch pallet and switch to the CMYK sliders you will see that it is not truly total black… that would be 400% ink density with 100% of all four colors. It is what they call a “rich” black, usually the following formula:

  • Cyan- 75%
  • Magenta- 68%
  • Yellow- 67%
  • Black- 90%

That equals a total ink density for black, the darkest of all the colors, at exactly 300%. This is usually good for most printers, but if you notice a grayness and lack of contrast to your images from a client that will be a recurring one, you might want to ask about the ink density their print process allows. Not that you can change it, but by coloring with that ink density as the max in a custom color profile, you can avoid the washing out of other colors as well as your blacks by avoiding having them do a color profile conversion themselves.

This is the kind of stuff production people have to deal with all the time, and if you can avoid having them change or convert your image you will end up having more control over the final results… leading to less surprises when the illustration hits the stands.

Some Google searches on “matching screen to CMYK print colors” and “calibrating an RGB monitor for CMYK printing” will bring you a host of useful articles.

Thanks to Seth Wilks for the question. If you have a question you want answered for the mailbag about cartooning, illustration, MAD Magazine, caricature or similar,¬¨‚Će-mail me and I’ll try and answer it here!

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