Re: Colorsync-users Digest, Vol 5, Issue 209
Re: Colorsync-users Digest, Vol 5, Issue 209
- Subject: Re: Colorsync-users Digest, Vol 5, Issue 209
- From: Todd Shirley <email@hidden>
- Date: Sun, 15 Jun 2008 23:16:42 -0400
Hey Brian & Roger
I was always told that a big factor in the ink savings is the
increased dot gain of FM screening. Dot gain (TVI, whatever) is a
function of total dot circumference, so when you have lots and lots of
tiny dots (FM), there is more "edge area" than a lesser amount of big
dots. So the ink spreads more and less ink covers more area. Another
factor is that the total ink thickness on smaller dots is both less
thick and more even (from edge to center), which results in more
efficient color reflection with less ink. Or at least those are the
concepts as I understand them. It's a similar effect with concentric
screening and I even AM screening when the dots get very small (300
lpi or greater).
Here is a link to a PrintPlanet thread that starts out about
concentric screening but then goes on to explain all sorts of
interesting physics about different dot sizes (with some great
illustrations as well): http://printplanet.com/discuss/thread.jspa?messageID=10465⣡
-Todd Shirley
On Jun 15, 2008, at 7:09 PM, Roger Breton wrote:
Brian,
As amazing as it sounds, that's the sad truth.
I've personnally witnessed this very phenomenon on press.
Start with AM plates, run a number of sheets, adjust SID. Then stop.
Change
over to FM plates, start again and observe how all ink keys must be
closed
down, by a sizeable amount, in order to obtain the same color.
Regarding Roger's comments...
Why would switching from AM to FM result in an ink savings?
You're putting down the same dot area, and that would result in
approximately the same amount of ink being put on the paper.
The only thing that changes is the formation of the tonal
information:
a clump of machine spots vs. a pseudo-random distribution of the same
machine spots.
If you were to calculate the area of paper covered by ink per cell in
an AM halftone and compare that the area covered by ink per cell with
an FM screen, they should be the same, or very close, otherwise the
image would be different.
I am eager to hear the explanation.
Best wishes,
Brian P. Lawler
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