Total Ink Coverage based on what? - ECI-EN

29 Mar 2008

      I am new here. Hi all of you! 

Here is my first contribution; a question regarding: 

Total Ink Coverage, TIC, for offset printing and the ink limits:

In the past, when I worked in a analogue photographic enlarger, the TIC was not open for
discussions: we could not alter it.

When we bought a drum-scanner and where able to handle the values (and not colours, by the
way) electronically we where now able to decide what TIC we wanted.
The TIC's used where based on what people from Crosfield, Hell etc told us was
"good".
For coated offset printing values around 375% where often used. Same for uncoated and even
for newsprint sometimes (at least in my company) until we learned more, usually from other
people in the biz, and then we lowered the values for uncoated qualities.

Conclusion so far: TIC's where based on opinions and experience.

Photoshop and other softwares where introduced and followed the pattern as with the
drum-scanners.

ICC-technology appeared. Good ideas but not very high quality until maybe five years back
in history, generally speaking. 
Initially the ICC-technology created more "colour gurus" rather then good
quality.
TIC's still based on opinions, "gray hair" and "experience".

Some people in the biz started to alter values for TIC, often based on test-strips with
CMYK, from 400% and down: visual checks etc.

Now:
For several years we have had the technology to actually calculate the best possible TIC
in a scientifical manner but still many colour gurus use the "good old default"
values. For example: 300 to 350 for coated, 260 to 319 (ECI) for uncoated and 220 to 240
for newsprint. 

Why do we not calculate the TIC's scientifically? Today we have the tools, I have the
tools and we use them. 

One example: for coated offset printed within ISO standards we base a neutral black on
around 340-350% and we reach L=10. 
...
 From that we allow the calculation to deviate delta 1
in L, not in a or b. A engineer that I work with called this method JND, Just Noticeable
Difference. This way we reach a TIC in neutral black that is 233% (two hundred and
thirty three)! In other words: we print neutral black with L=11 with 233%.
Note: This technology do not set the TIC limit to 233 for all colours, it is indvidual. A
dark red can for example end up 244%. Normal ICC-profiles are in other words a compromise:
the TIC will limit all colours to one top value for TIC.
One more example: for newsprint we have reached a TIC, for neutral black, around 180% with
a better L-value then ISOnewspaper26v4 - but a dark red can in the same print reach 209%.
And so on.

So, good bye to "opinions", "gray hair" and "experience" or
what is your opinion and experience regarding TIC?

Best regards
A Sebastian