Default Spot Screen Angle

Started by Tracy, March 10, 2021, 12:48:52 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Tracy

anyone know how to find what angle the Default Spot Angle is? XMF

We have a job we have printed for 15 years different presses different line screens
and no problems, this went out to an outside printer and an image moire'd
we have had these printed at other printers without problems also

the image is a scanned 1200 dpi, 1 color
I see that they did use a different screen angle in the printed piece
I'm sure you smart guys can give me some insight on why this happened!


born2print

#1
If the image is only 1/c, there should be no possibility of a moiré at any angle...
unless the scan was a re-screen and the moiré is in the image.

If the image was more than 1/c, the usual suspect is that the default non-process color angle is the black angle and it needs to be changed for that job.

DCurry

If it's a 1-color job, I doubt very much that the angle matters other than some angles will give you jagged sawtooth edges along screened areas (we use 45 degrees to make edges clean.) What may have happened is the plate was imaged at a res that is not evenly divisible by 1200, or perhaps the 1200ppi image got re-sampled somewhere in the workflow.
(Dammit, born beat me to the punch as I was typing!)
Prinergy 8.4.1.45 • Preps 8 (Not a fan) • SmartStream Designer

Build a man a fire, and he'll be warm for a night. But set a man on fire, and he'll be warm for the rest of his life!

born2print

"What may have happened is the plate was imaged at a res that is not evenly divisible by 1200"

Whoa, like a machine-pixel moiré... that sounds so crazy it just may be true!

David

what about 2540?


that used to be the default res... in the olden days
Prepress guy - doin' jobs one at a time
www.texasgraphics.com

born2print


DCurry

That's what I was thinking. I also worked at a book publisher a few years ago and they still ran film, and on big jobs would image the film at lower res to make it image faster.
Prinergy 8.4.1.45 • Preps 8 (Not a fan) • SmartStream Designer

Build a man a fire, and he'll be warm for a night. But set a man on fire, and he'll be warm for the rest of his life!

Joe

Quote from: david on March 10, 2021, 01:45:00 PM
what about 2540?


that used to be the default res... in the olden days

Yep. 2540 / 1200 = 2.116666666666667 =  FAIL.

2400 / 1200 = 2 = SUCCESS.
Mac OS Monterey 12.4 | (retired)

The seven ages of man: spills, drills, thrills, bills, ills, pills and wills.

born2print

Since we're throwing out crazy theories...
does the paper have a textured pattern?
:banana:

Joe

I don't think the math is a crazy theory. Back in the day when we were switching from shooting paper on a camera to instead scanning a screened print we would scan it as line art at a value that was half (1270) of our filmsetter resolution (2540) and it worked great. If we scanned it at 1200 or any value that wouldn't go into 2540 evenly we would get a moire. Of course that was for screened images. With screened images the filmsetter would not re-screen it if it was a value that was evenly divisible into 2540 and it would use the existing screening in the image. But if it wasn't a value that was evenly divisible into 2540 it would try to re-screen the screen which produced a moire.
Mac OS Monterey 12.4 | (retired)

The seven ages of man: spills, drills, thrills, bills, ills, pills and wills.

born2print

You're right, I guess I meant "crazy" as in brilliant / less obvious... like "wow - that's crazy!"
My paper idea on the other hand, that's just crazy.

Joe

Quote from: born2print on March 10, 2021, 03:04:39 PM
You're right, I guess I meant "crazy" as in brilliant / less obvious... like "wow - that's crazy!"
My paper idea on the other hand, that's just crazy.


I've seen crazier things in this business. :rotf:
Mac OS Monterey 12.4 | (retired)

The seven ages of man: spills, drills, thrills, bills, ills, pills and wills.

born2print

I mean hey - that's how lenticular works, right David?  :sarcasm:

David

yes, the altering the output res is how you adjust/scale the lenticular file to fit the plastic.

thank you Kodak

it's been a while since I did any of that.

:old:
Prepress guy - doin' jobs one at a time
www.texasgraphics.com

David

Prepress guy - doin' jobs one at a time
www.texasgraphics.com