Re: Dot shape prevalence
Re: Dot shape prevalence
- Subject: Re: Dot shape prevalence
- From: Rich Apollo <email@hidden>
- Date: Fri, 7 Oct 2005 09:07:52 -0500
On Oct 6, 2005, at 10:34 PM, email@hidden
wrote:
I'd like to hear more about the composite dot. What shape(s) did it
take
on over the range of tonal values?
Scitex's composite dot runs from round in the highlight to elliptical
in the quarter tone to square in the mids and back to round in the
shadows.
The reason behind placing magenta at 45 degrees is so that you have 45
degrees between the angle of the yellow and the angle of the magenta
(with yellow normally being at zero degrees). The problem with black at
a non-45 degree angle is that you can see saw-tooth. I want the best of
both worlds, so I use a screen/angle set that puts cyan at 15 degrees,
magenta at 75 degrees, yellow at 30 degrees, and black at 45 degrees.
So
I get 45 degrees between magenta and yellow and keep black at 45
degrees.
With AM screening your gonna' get moire somewhere. With 105º C or M,
90ºY, 75º C or M, 45º K your moire is most likely in tan to red tones
(fleshtones). Move the yellow to 60º and now the moire occurs in
greens. Couple that with the fact that 90º is gonna' show the greatest
amount of noise, patterning, etc. Agfa, in the past, ran the yellow at
a higher line screen than the other colors and rotated the yellow
angle. I've heard of several shops running AM screening for C, M, and K
and FM for Yellow to combat moire.
There should not be any saw tooth on
a black at either 75 or 15 degrees and as the black is the lightest
lay down
of colour - under normal circumstances - many printers in the UK used
to ask
for those angles.
That holds for imagery, but not for things like type or flat tints of
gray. The 45º is optically smoother and reduces the incidence of edge
effects.
Rich Apollo
314-344-1144
email@hidden
www.prioritylitho.com
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