Banding Problem

[ruthndul]

Hi,

Looking for expert advice here.
We have banding problem.

a job that previously been done on offset press with Pantone 653U (uncoated) (see 2nd sample from the left)
now done on digital (see 3rd sample from the left)
We did our best to match their business card which was done on coated, Pantone was adjusted to 653C.
However, customer doesn't like the pinkish gradient on the lighter side (circled).

The job was tried to be redone on the offset press.
Another problem occurred : banding (see first sample from the left).



Things I've done and didn't work
- convert the gradient to bitmap in photoshop
- adding gaussian blur and noise to the bitmap in photoshop
- rotate 90 degree when outputting to plate
- rotate gradient 1 degree
- increase line screen from 150lpi to 175lpi
- reduce the max gradient from 100% to 90%

The last one (4th from the left),
I created a bunch of blending objects to ease of the gradient computation while reducing the magenta amount on the lighter side.
We haven't try to output the last one to plate, as the original is only one spot colour, and for digital output purpose, I convert it to CMYK.

File was created in Indesign CS6
exported to PDF for output

Digital : Xerox 700
Offset : Itek 3395 2 color
Plate maker : Agfa Avantra 25 - polyester plate
RIP : Harlequin

Any ideas how to solve this problem ?
Thank you

 

[gordo]

This might be totally off the wall, but, have you tried converting the PMS color from spot to CMYK by modifying your CMYK settings to "custom" and "Maximum Black" "GCR"?

 

[gig0]

Sounds like a typical day in digital when it comes to dealing with gradients that are close to reflex blue. This is an example of the benefits of having a curve table/gradation tool (as Creo likes to call it) on the front end; so you can lower the magenta value at the bottom quarter of the curve on the fly. It's really not that uncommon.

 

[ruthndul]

This might be totally off the wall, but, have you tried converting the PMS color from spot to CMYK by modifying your CMYK settings to "custom" and "Maximum Black" "GCR"?

Thanks Gordo,

I think converting spot to CMYK and modifying CMYK setting is what I've done on sample #4.

Where can I find the option about maximum black GCR ?

 

[gordo]

Thanks Gordo,

I think converting spot to CMYK and modifying CMYK setting is what I've done on sample #4.

Where can I find the option about maximum black GCR ?

This is based on the "just get 'er done" theory of prepress.

I did a quick monotone gradient of 653 in PShop then did these steps to convert the Monotone to CMYK (download to make more legible):

The original CMYK using PShop's defaults had 20% Magenta in the 1/4 tones (Download and measure the following images).

But the MAX GCR had only 9% Magenta in the same 1/4 tones.

I don't know if this will help you but it might be worth a try.

 

[ruthndul]

Thanks Gordo

You Rock !