Re: Dot Gain mathematical Formula
Re: Dot Gain mathematical Formula
- Subject: Re: Dot Gain mathematical Formula
- From: Henk Gianotten <email@hidden>
- Date: Thu, 31 Mar 2005 00:34:00 +0200
At 16:50 30-3-2005 -0500, Terry wrote:
The TRICK is knowing what the desired or target condition should be. You
could use "SWOP" or "GRACoL" as a guideline or something else. But the
catch is that most specs are only at the 50% dot and not for the complete
tone curve. To complicate matters, a press printing at the "proper" dot
gain spec will/should not have linear or balanced behavior. By "balanced"
I mean a certain amount of gain at the 50% with equal but less gain at
both the 25% and 75% aimpoints. No, a press will/should have a bit more
1/4 tone gain relative to the 3/4 tone but you won't find a specification
for this anywhere AFAIK. For my own press profiling work, I've analyzed
typical press behavior and have my own adjustments that I apply to 1/4,
mid and 3/4 tones from which I then derive a smooth curve. This is sort of
the "magic decoder ring" if you will. And even armed with this
information, it still comes down to charts and graphs to get from the
press acutal to the desired behavior if the RIP doesn't do this for you.
Cheers,
Terry
Hi Terry,
These "scientific controlled" calculations for TVI exist.
For the ISO 12647-2 TVI the German Fogra Institute created a TVI scheme for
the 5 different paper types.
The 5 descibed in the ISO 12647-2 standards.
They defined the TVI sets for CMY and a different one for K.
Depending on the paper conditions the absolute TVI peak differs.
These conditions are described in the PSO (Process Standard Offset)
released by the BVDM (German Printers and Prepress Asociation).
The book is a very detailed description how to establish your own in-house
standards based on the ISO standards.
The result is a product (better said, process) that complies to the ISO
12647-2 standard.
Some 60 German offset printers are now fully certified by Fogra and BVDM
and are able to deliver printed products within these new tight specs.
Some 3000 companies invested in the PSO publication (book and cd-rom) to
learn how to standardize the process.
Even their proofs are ISO certified.
And all of them use spectrophotometers to read the colors on proof and press.
It's a pity that all this great information is only available in the German
language.
At this moment only German, Swiss and Austrian printers and print buyers
benefit.
And a few Dutch, Danish an Polish printers who can read German.
Regards, Henk
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