Re: Dot shape prevalence
Re: Dot shape prevalence
- Subject: Re: Dot shape prevalence
- From: Rich Apollo <email@hidden>
- Date: Mon, 10 Oct 2005 09:13:01 -0500
On Oct 8, 2005, at 2:04 PM, email@hidden
wrote:
Funny you mention it. When I look at the dot shape out of an AGFA CTP,
with
a 10x loupe, it's plain to see that even though it says "2400 dpi" on
the
box, the dot shape is not all that *sharp* if you ask me, unlike the
traditional film-based so-called hard dot. For example, take a 10% 150
lpi
AM "round" dot. Well, the shape of that dot is anything but nicely
circular:
it is circular "in intention" but it has a highly irregular geometry,
akin
to a circle scan with a too low resultion having the appearance of a
collection of tiny-itty-bitty pixels all bunched together, randomly
sticking
out of the "main" shape in every direction. If that's what "state of
the
art" in halftone screening mean, in current workflows, and I'm talking
Prinergy, Harlequin and Rampage here, then I say we've actually taken
a step
backward in quality.
Roger, you're gonna' have to get a more powerful glass/scope to review
this kind of thing. What you're seeing could be the result of many
things โ I'm leaning toward plate grain. I don't know the precise
measurements for 150 lpi, but I was just reviewing a 10% patch at 170
lpi. It's about 40ยต โ this is much larger than the minimum spot size
for a 2400 dpi device. The dot you're looking at is comprised of
several spots (the laser spot size is constant) so, yes, there will be
some stair-stepping to the edges โ but we're talking TINY. Tiny to the
point that you shouldn't be able to see it with a 10X loupe. I've got a
75X and a 2400 dpi plate setter and those dots are CLEAN.
The clean character of CtP dots is, from what I've read/heard/been
told, the primary reason for the lower dot gains associated with CtP.
I really suspect you're seeing some characteristic of the plate or
chemistry.
Rich Apollo
314-344-1144
email@hidden
www.prioritylitho.com
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