ICC Profiling Basics
ICC Profile's are an International standard set of colour targets, that allow the exact same colour to be reproduced in all printing processes and electronic visual devices. This can be done by using a spectrometer to read the LAB value. A LAB colour space is a colour-opponent space with dimensions "L" for lightness with "a" and "b" depicting the colour-opponent dimensions based on non-linearly compressed (e.g. CIE XYZ) co-ordinates. The terminology originates from the three dimensions of the Hunter 1948 colour space, which are L, a and b.
Why we need ICC Profiles?
As humans we perceive colour differently from one another (colour blindness is one of the reasons over and above the fact that your eyes just do not see all colours). ICC Profiles remove the human error in seeing colour, by using a Spectrometer device that can read the colour and give a value indicating whether the colour is correct or not. The value is known as Delta E ( E - (Delta E, dE) which is the measure of change in visual perception of two given colours. Delta E is a metric term used in understanding how the human eye perceives colour difference (The term Delta is derived from the mathematical term meaning change in a variable or function). The Delta E value indicates how far out you are in a positive or negative value when reading the LAB colour. An ICC Profile forces all printing processes and electronic visual devices to reach the same Delta E value (as close to 0dE) as possible. Delta dE value of 0 dE to 2 dE will not be detected by a trained eye, however, from 2 dE to 3.5 dE will be noticed by the trained eye. 4 dE and upwards will be detected by most untrained eyes. ICC Profiling also allows you to print the same image anywhere in the world using an ICC Profile calibrated printer ensuring the exact same result with a Delta E of 0 dE to 2 dE.
What are the differences between all printing processes and electronic visual devices?
Printing processes use CMYK (Cyan, Magenta, Yellow, Black) and spot colour inks known as Pantone and GOE colours to produce the final product. Monitors, TV's, Cameras, Video Cameras, Scanners, Cell phones, tablets and electronic billboards all use RGB (Red, Green, Blue). The fact that your monitor is a RGB visual and your printer prints in CMYK is problematic in that the printercannot produce all colours. The reason for this is that the RGB colour spectrum is larger than the CMYK spectrum and both are smaller than the human colour perception, Look at the image on the right.
RGB Monitor
CMYK
Print
How does this affect you?
In today's electronic world we all take Photos and Videos without the understanding of how ICC Profiles work and are preset on the devices. These devices will look like the picture on the left, vibrant and colourful, but once you print it on your desktop printer you notice a visual difference. This is because your device produces images in RGB and while your printer produces prints in CMYK. Both the device and printer are not properly calibrated with a suitable ICC Profile. We can deduce from this exercise that, an exact same quality picture using either RGB or CMYK cannot be attained. In order to remedy this an ICC Profile standard in CMYK can be set. In the printing Industry "Fogra 39" is used. Once the profile is loaded for your printer and you print an image the printer recognizes the Fogra 39 workspace and will ensure that the correct colours are used in producing the image, however the paper that is used to print on is not calibrated to the same workspace. Paper handles ink in different ways, if an image is printed on standard bond paper the ink will saturate the paper and give you a darker flatter looking print, but if you used coated print paper, either matt or gloss the ink will not saturate the paper as much as it did with the bond paper. The paper as well as the calibration of the printers ICC profile allows us to produce the exact image as we see on top right. Please note that there will still be a difference in the colour because of the difference in colour space.
After calibrating the printer and producing a printed proof, a plate for printing to Litho, Flexo, Gravure, Dry-offset and Silkscreen can be produced. This file can be forwarded for the production of a plate "Fogra 39" or the appropriate ICC Profile for the process intended.
Each Printing press will also have a profile that matches the press or the press target. This is called finger printing (checking what the machine will produce with the ICC Profile intended for that press). This will be checked with a spectrometer.
Written by P.M. Welman
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