Best screen angle for one color gradients

[Macmann]

Do you have a favorite screen angle for one color gradients or is it artwork specific? In your opinion what affects the quality of the gradient more, the lpi, mesh count, or angle? 7.5? 22.5? 52.5 or 82.5? Does angle even matter with a one-color gradient? What about dot shape? Elliptical? Round? Rugby? Do you use a special ink or process for gradients? They always seem to be a challenge. Thanks in advance for your input.

 

[Repro_Pro]

Screening is visually least noticeable around 45° angle.
LPI and mesh should go hand in hand, choose combinations from mesh manufacturer tables.

 

[gordo]

As Repro_Pro wrote, screening is visually least noticeable around 45° angle.
The best AM dot shape (not just for gradients) is Round - i.e. non-transforming - round through the tone scale.

BTW - Are you flexo or screen printing? (the 7.5 degree offset)?

 

[Macmann]

Sorry-screen printing. I was always led to believe that a 45° angle would set up a mesh moire? Gordo, as you've explained in the past the closest thing Esko has to round is the Circular option. We are currently trying this dot shape. We had been using Elliptical for years but it just seems to be a challenge of late. I suspect the new LED inks are contributing. We usually print one color gradients-all different colors. 55 line screen is our most common lpi. Thanks for the input guys!

 

[Magnus59]

As Repro_Pro wrote, screening is visually least noticeable around 45° angle.
The best AM dot shape (not just for gradients) is Round - i.e. non-transforming - round through the tone scale.

View attachment 291342

BTW - Are you flexo or screen printing? (the 7.5 degree offset)?

We have used a 7.5 degree offset for over 20 years for litho printing
With your background Gordo, you must be aware that it was recommended by Scitex back in the Brisque days and we carried it through to Prinergy.

 

[gordo]

We have used a 7.5 degree offset for over 20 years for litho printing
With your background Gordo, you must be aware that it was recommended by Scitex back in the Brisque days and we carried it through to Prinergy.

The standard photomechanical screen angles do not work best with digital screens. As a result some output device, halftone dot shape, screen angle and frequency combinations can result in moiré within one screen resulting in "single channel moiré."
One solution to avoid this problem was the development of shifted angles. The angular distance between screen angles remains more or less the same however all the angles are shifted by 7.5°. This has the effect of adding "noise" to the halftone screen and hence eliminating the moiré.

 

[halmac]

I miss those days. Taping down all those screens on mylar. Picking out the dots with your pointed tool when you got a speck on the glass. Chokes and spreads. Rubylith. Chromalin proofs. Velox prints.

 

[gordo]

I miss those days. Taping down all those screens on mylar. Picking out the dots with your pointed tool when you got a speck on the glass. Chokes and spreads. Rubylith. Chromalin proofs. Velox prints.

I love the smell of rubber cement in the morning. Smells like...paste-up time!

 

[chriscozi]

I miss those days. Taping down all those screens on mylar. Picking out the dots with your pointed tool when you got a speck on the glass. Chokes and spreads. Rubylith. Chromalin proofs. Velox prints.

Cut right to the chase - wet etching pan film . . . .

 

[schenkadere]

We have used a 7.5 degree offset for over 20 years for litho printing
With your background Gordo, you must be aware that it was recommended by Scitex back in the Brisque days and we carried it through to Prinergy.

I'm an old Scitex guy back to the days of Imagers and Erays, way before Brisque, and we always ran the 7.5º shift.

 

[gordo]

I'm an old Scitex guy back to the days of Imagers and Erays, way before Brisque, and we always ran the 7.5º shift.

We have used a 7.5 degree offset for over 20 years for litho printing
With your background Gordo, you must be aware that it was recommended by Scitex back in the Brisque days and we carried it through to Prinergy.

It is not that a vendor recommends using a particular screen set, nor that you used a particular screen set for years that's the important thing - but WHY.
Your vendor should be able to give you a technical-based reason as to why a specific screen set should be used. The same goes for historical use - just because you've been doing it a certain way for years does not make it correct.
For example, back in the days of roll film imagesetting certain screen sets were recommended by the vendor. The reason? Because those screen sets would hide film imaging artifacts caused by the roll feed. But they wouldn't tell that to their customers.