Color Management Myths 1-5

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ColorNews

This reserved article originally appeared in CHROMiX ColorNews Issue 9 on October 22, 2003.

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colornews(at)chromix.com to subscribe to the ColorNews newsletter.

by Steve Upton


Five Color Management Myths I keep running across "understandings" in the field, the media and on the Internet. It seems like a crime to let these statements and confusions pass without some attempt at clarifying them so I have tackled a few of the more common ringers I've been hearing.

Contents

Myth #1: Color Management is not useful in CMYK-only workflows

"We can't use color management, we're a CMYK shop" I can't tell you how many times we've heard this. While many shops work fine in CMYK-only mode, they can certainly benefit from color management in several ways:

  1. Hard Proofing - creating effective press simulations on an inkjet is a challenge. If you don't use ICC profiles for the task it can be VERY difficult. I have been told by a number of printers that they have no color management in-house and yet they use inkjet proofing. After a little investigation they are surprised to discover that ICC profiles are in use in their RIP creating their proofs. Sometimes it's all been setup by "the vendor" and they didn't realize how it worked but they are missing out on other opportunities as well....
  2. Soft proofing - if the simulation profile from the proofing RIP is moved onto the workstation and setup properly in Photoshop, soft proofing can get quite accurate on a calibrated display. Hand that profile off to your customer and their soft proofing will improve significantly - so will their expectations. Moving color management upstream to the creatives gets the "reality check" of press gamut limitations in the hand of the people that need it. This arrives at a printer's counter as a much more realistic customer.

and no CMYK is harmed in the above procedures....

Myth #2: There is some internal Lab/Color reference that the output of printers is compared to when profiling

I have heard it time and time again. "First the target is printed, then the output is compared to the color that should have appeared. A profile is calculated to correct for the behavior of the printer."

Wrong.

Unlike a strict, conformist military academy, profiling a printer does not find out how a printer performs and then force it to conform to a certain behavior. Its much more like a hippie commune. The innate abilities of the printer are discovered and then a translation table is written to convert from the desired colors (Lab) to the RGB/CMYK settings most appropriate for the printer. This may sound like splitting hairs but it makes a big difference. When profiling a printer it is best to tune it up to the best of its abilities - regardless of the fact that you may want to limit the gamut later using a proof or press profile for proofing purposes.

Myth #3: The gamut of RGB is larger than CMYK

RGB = big gamut 
CMYK = small gamut

Right? Wrong.

As illustrated in our last ColorNews newsletter, overlaying an RGB gamut with a CMYK gamut often results in overlap much like drawing a circle over a triangle. Bits of the triangle (RGB) extend outside the circle AND bits of the circle (CMYK) extend outside of the triangle.

This means that there are RGB values that cannot be printed on press - no surprise there. BUT it also means there are CMYK values that are often outside of the gamut of RGB. So sRGB, Adobe RGB (1998) and your monitor RGB spaces will typically not show/contain all the colors (especially Cyans and some press Yellows) that can be printed on press.

Most inkjet printers used without a RIP are accessible using only RGB. Even though the printer uses CMYK or CcMmYK, due to operating system limitations, your application can only speak RGB to it.

Does this mean that the gamut will be affected by the use of RGB?

No, whether you print to a printer using RGB or CMYK, the choice of one over another should not affect the gamut. That said, using a RIP may allow you to change your inking and enlarge the gamut. While you will access this larger gamut via CMYK it is not CMYK itself that gets you the bigger gamut... you'll just have to trust me on this one.

Myth #4: A profile is for calibration

Calibration is monkeying with your device to get it to some known, repeatable behavior (see military school, above). Setting a monitor to 6500K and gamma 2.2 or linearizing a printer is calibration. This is an important function and closely related to Color Management but it is NOT color management.

Once you have calibrated your device, then you build a profile for it. In the case of monitor profiles, the calibration curves from the graphics card are often embedded into the profile for safe keeping. This might seem to blur the line between calibration and profiling but pay no attention to that. The profile describes your wonderful device's behavior to the rest of your color-managed workflow so all your devices can get along and color can travel through your workflow un-harassed.

Myth #5: 5000K on a monitor is the same as 5000K in a light booth

Why this is not the case is a particularly involved answer. As I mentioned in issue #2 of ColorNews, it simply isn't so in most cases and the why's are outside the scope of this article.

Suffice to say that if you have a good-quality light booth such as one from GTI, the lights in the booth are typically fairly close to 5000K. Close or not, if you choose to have your booth near your display then you are choosing for it to be your white standard. If you calibrate your display to 5000K you will probably find that the white on display does not match a piece of paper in the booth. Try calibrating to 6500K or some other white point until you get closer. It is not a sin to tweak the white point using controls on the front of your display. Just remember that you'll have to do it each time you re-calibrate. This is one of the reasons why monitor calibration software with a wide range of color temperature settings is a better option. Something to think about at upgrade time...

For more Color Management Myths, see Color_Management_Myths_6-10

List of all color management myths

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