Do not use CMYK values to communicate color: Part 2 the follow up

This is a follow up to my last article. Thought it was important to show specifically what I was describing within RIP software. I will show how CMYK values will change based on the output profiles (calibration of the device). Keep in mind this also means every time you update an output profile (calibrate your device) the values will change as well.

I will show two output profiles for the exact same Pantone colors. One is a profile created with Coated stock. The other was created with Uncoated stock. I’ve named them Gloss and Matt respectively. Further, I chose Pantone 185 C as the sample color.

There is something that is a bit off in my samples. Everything is accurate. However, there is something that should be opposite of what is actually shown. I would love to see if someone picks up on it. If you spot it please add it to the comments of this article. (Yes, pun was intended)

In the examples below, I mark four areas. From top to bottom and left right they are: 1. Output Profile 2. Delta for accuracy 3. L*a*b* values 4. CMYK values. I will refer to these the rest of the article.

Note the differences in these images. Three out of the Four marked areas have changed. The only one that stayed the same is the L*a*b* (Original). The reason for this is that the L*a*b* color space is the only device independent color space. Everything else is device dependent. Therefore, the CMYK values will have to change based on the icc output profile and the current state of the device.

Another way to say this is: as your scanner, monitor or printers age you must update your calibration profile in order to maintain accurate color. The pixels in your monitor don’t shine as bright over time. Therefore, the calibration must compensate for this to maintain accurate color. The CCD array in scanners don’t capture as much data over time. Same can be said for Drum scanners as well.

Printers are exactly the same way. Over time the color shifts due to maintenance, humidity and temperature. Therefore, we must update the calibration (output profile) in order to maintain color. Essentially, we are shifting the CMYK values to compensate for the changes in the device.

The way we manage this is through the profile connection space. The source profile is compared to the output profile and brand new CMYK values are created. Thus, my example in the previous article of printing 100% Cyan is validated.