Screen angle for CMYK

[NicolasD]

What do you use??
We are using the same angles since we started and i think there must be something better. Any slight variation in the register appears straight away on the images.

 

[toronar]

We use
C 15°
M 75°
Y 0°
K 45°
for ages now. I doubt that it will ever change

 

[gordo]

What do you use??
We are using the same angles since we started and i think there must be something better. Any slight variation in the register appears straight away on the images.

Lots of screen angle info here: Quality In Print

This post in particular: Quality In Print: Halftone screen angles - part 2 of 3

However you say you are experiencing tone/color shifts with slight variation in register so, IMHO your problem is likely resulting from what happens to rosettes when misregistration occurs rather than screen angle issues. See here:
Quality In Print: Rosettes

That can be solved by changing your separation (e.g. heavy GCR) or screening methods (e.g. going FM).

best, gordon p

 

[marktonk]

Here is a link to a book on Heidelberg Screening. This will show you what angles we use depending on screening. Not all screening is the same so may or may not be applicable to what you currently use.

Heidelberg - Download Center

Regards,

Mark

 

[pacificiam]

y is 90 coz it is least visible colour
k45 its most darkest colour and least visible angle to human eyes

for C & M angles r interchanging btween 75 or 15

 

[gordo]

As noted before, screen angles are neither the cause nor the solution to NicolasD's original question.

"Any slight variation in the register appears straight away on the images."

Color shift with misregistration is more than likely resulting from what happens to rosettes when misregistration occurs rather than screen angle issues. This explains it:
Quality In Print: Rosettes – everything you didn't realize you needed to know - part 2 of 2

That can be solved by changing the separation (e.g. heavy GCR) method or screening methods (e.g. going FM).

best, gordon p

 

[NicolasD]

Impressive site gordo, really usefull

 

[Lukas Engqvist]

On Screen angles and varnish
Some jobs are too heavy on ink for production time, this means they have problems drying. Especially for uncoated paper. For a period of time we tried to avoid this by outputting varnish at 80% raster (full raster means more "goo*" on paper and can some times seal so that ink takes even longer to dry). For some jobbs this is fine but for others... and this is where the raster question comes... we get moiree.
Printing full varnish eliminates moiree, with the afforementioned downsides.

The question is if I have a standard rosette for CMYK, how do I find an angle for the varnish? By default I put spot colours in magenta angle (this because black + one spot is the most common) second spot I put on cyan. But have no idea what would be a good varnish angle (defaults on magenta at the moment)
( CMYK defaults 15, 75, 0 45)

Hope this isn't hijacking the tread but that you consider the understanding of screens as a related topic

*by goo I mean all that stuff that isn't pigment, don't know if there is a technical term for it. Felt TAC was a too strong term since I don't know if varnish is an Ink.

 

[Bret Hesler]

On Screen angles and varnish
...
The question is if I have a standard rosette for CMYK, how do I find an angle for the varnish? By default I put spot colours in magenta angle (this because black + one spot is the most common) second spot I put on cyan. But have no idea what would be a good varnish angle (defaults on magenta at the moment)
( CMYK defaults 15, 75, 0 45)

If you put it on the Yellow angle, you should not get any more moire than you get from the Yellow. Another option would be to use stochastic for the varnish if you have it as an option.

Bret

 

[gordo]

Impressive site gordo, really usefull

Thank you! Rummage around the blog and check back often.

best, gordon p

 

[Lukas Engqvist]

Interesting, was a little afraid of using yellow thinking it would increase the yellow moire, I know there is an "error diffusion" alternative but havent tried it for anything... yet

 

[gordo]

Interesting, was a little afraid of using yellow thinking it would increase the yellow moire, I know there is an "error diffusion" alternative but havent tried it for anything... yet

If you decide to use an FM screen make sure it is a coarse (about 35 microns) second order FM (dots might form "worms" in the midtones). This will have a dot gain profile similar to your AM raster. If it is a fine first order screen (which is suggested by the "error diffusion" name) your plate/press combination might cause a mottle effect. (different FM dot shapes explained here: Quality In Print: FM Screening Dot Shapes/Patterns )
You could also use a 35 micron second order FM for the Yellow (quite common practice) and a standard AM screen for the varnish.


best, gordon p