HP Indigo screen angles

[MacTwidget]

Would anyone be able to educate me on the screen angles that HP uses on their Indigo presses?
Cyan = 4°
Magenta = 64°
Yellow = 18°
Black = 34°
Is there a reason for this?
Has anyone printed with traditional angles?

 

[gordo]

Would anyone be able to educate me on the screen angles that HP uses on their Indigo presses?
Cyan = 4°
Magenta = 64°
Yellow = 18°
Black = 34°
Is there a reason for this?
Has anyone printed with traditional angles?

This is speculation...
Those angles maintain the traditional 30 degree separation between K, M, and C and the near 15 degree split for the Y. So in that sense the angles are conventional. Generally when an output device does not use the "traditional" angles it is because the device has it's own harmonic frequency when imaging. Therefore the engineers rotate the screen angle set by some degrees so as to avoid the screens harmonically beating with the output device's frequency which would cause either moiré or artifacts in the final output.

Best, gordo

 

[MacTwidget]

This is speculation...
Those angles maintain the traditional 30 degree separation between K, M, and C and the near 15 degree split for the Y. So in that sense the angles are conventional. Generally when an output device does not use the "traditional" angles it is because the device has it's own harmonic frequency when imaging. Therefore the engineers rotate the screen angle set by some degrees so as to avoid the screens harmonically beating with the output device's frequency which would cause either moiré or artifacts in the final output.

Best, gordo

Thanks Gordo!
You might be right...

Unfortunately with their screening angles, tints with Cyan and/or Black look very bad at any edges that are perfectly vertical or horizontal.

 

[mutti8000]

Gordo is right, it's a reminiscens from the older Indigos that had badly designed writing heads and all kinds of banding problems..
They used the trick with the non standard angles to "hide" the shortcommings of the press.
I think that the issue you are experiencing, with the jagged edges, is due to the rather low resolution (DPI) of the writing head.
Let me guess it's an old 3050 or 5000 press? If it is, my post should be spot on

 

[MacTwidget]

Gordo is right, it's a reminiscens from the older Indigos that had badly designed writing heads and all kinds of banding problems..
They used the trick with the non standard angles to "hide" the shortcommings of the press.
I think that the issue you are experiencing, with the jagged edges, is due to the rather low resolution (DPI) of the writing head.
Let me guess it's an old 3050 or 5000 press? If it is, my post should be spot on

You are correct.
We have both a 5000 and a 5500.

Do you know if this has been improved with the 7600?

Thanks for your reply!

 

[Chief_1975]

What happens when they are running Indichrome, CMYK Orange + Green etc ??

 

[meddington]

Unfortunately with their screening angles, tints with Cyan and/or Black look very bad at any edges that are perfectly vertical or horizontal.

Its been a while since I've worked with the HP Indigo 5000, but there is a feature called HP Adaptive Halftoning that can add a "halo" effect...dots to fill gaps around the edge of screens which can help minimize edge artifacts. Try turning this feature on an see if it helps.

 

[grapheeq]

As Gordon mentioned the screen angle difference is similar to the conventional screening (30 degrees). The jaggered edges of tints can be avoided in printing when you use those tints in 45 degree angle. But unfortunately this may not be a possibility on Hp Indigo.

The reason for the strange angle values is to ensure that the screen angles do not clash with the imaging head. As the imaging head is an array of LED imager. The principle is similar to Flexographic printing where you have the anilox angle influencing the angle of the half-tone screen.

Regards, Grapheeq