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Author Topic: Default Spot Screen Angle  (Read 6575 times)

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Offline Tracy

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Default Spot Screen Angle
« on: March 10, 2021, 01:48:52 PM »
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!


Offline born2print

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Re: Default Spot Screen Angle
« Reply #1 on: March 10, 2021, 02:10:08 PM »
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.
« Last Edit: March 10, 2021, 02:15:59 PM by born2print »
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Offline DCurry

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Re: Default Spot Screen Angle
« Reply #2 on: March 10, 2021, 02:21:29 PM »
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!)
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Offline born2print

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Re: Default Spot Screen Angle
« Reply #3 on: March 10, 2021, 02:25:18 PM »
"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!
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Offline David

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Re: Default Spot Screen Angle
« Reply #4 on: March 10, 2021, 02:45:00 PM »
what about 2540?


that used to be the default res... in the olden days
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Offline born2print

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Re: Default Spot Screen Angle
« Reply #5 on: March 10, 2021, 02:48:29 PM »
 :old:
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Offline DCurry

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Re: Default Spot Screen Angle
« Reply #6 on: March 10, 2021, 02:49:11 PM »
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.
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Online Joe

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Re: Default Spot Screen Angle
« Reply #7 on: March 10, 2021, 02:50:26 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.
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Offline born2print

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Re: Default Spot Screen Angle
« Reply #8 on: March 10, 2021, 03:02:09 PM »
Since we're throwing out crazy theories...
does the paper have a textured pattern?
 :banana:
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Online Joe

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Re: Default Spot Screen Angle
« Reply #9 on: March 10, 2021, 03:57:45 PM »
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.
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Offline born2print

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Re: Default Spot Screen Angle
« Reply #10 on: March 10, 2021, 04:04:39 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.
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Online Joe

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Re: Default Spot Screen Angle
« Reply #11 on: March 10, 2021, 04:19:07 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:
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Offline born2print

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Re: Default Spot Screen Angle
« Reply #12 on: March 10, 2021, 04:28:51 PM »
I mean hey - that's how lenticular works, right David?  :sarcasm:
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Offline David

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Re: Default Spot Screen Angle
« Reply #13 on: March 10, 2021, 04:54:28 PM »
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:
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Offline David

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Re: Default Spot Screen Angle
« Reply #14 on: March 10, 2021, 04:54:56 PM »
oh, lenticular sucks...

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