gradiation patches

[snrv]

Hi,
We use to print gradiations with out problems, but some images are getting steps in gradiation. we fine tuned our our curves to minimize the effect, we are using violet plates. The problem we have is when we send the same files to make plates outside(Thermal plates) printing is better than the original files and we can't find any steps in gradiation.
So we send some test files to make plates on thermal CTP and read the values and set our Violet ctp to get the same results. But printing is not matching to thermal plates.( the problem only with gradiation steps, quality wise violet is very good). please help me to fix this problem

 

[rich apollo]

There are several possibilities:

1) You may have too many control points in your linearization

2) Your RIP may not be up to the job. Outdated PostScript based RIPs had problems in how they rendered blends

3) Problems in the optics of your platesetter. Dirty optics or incorrectly set laser power could cause issues.

4) You may have an issue with your plate processor - bad chemistry, incorrectly set rollers, bad scrub roller covers, incorrect dwell time.

Anyhow, could be a host of issues.

 

[Bret Hesler]

I do see some banding in the image, which can usually be reduced with a little noise in Photoshop. However, if it is not a problem on a different system, then I would look into other causes.

I'll add screening to Rich's list. What RIP/ screening are you using?

And the thermal plates made elsewhere, Same RIP/screen set?

Bret

 

[snrv]

hi,
we can see some patches in original file, but same file is looks great on kodak thermal ctp, with same resolution and lpi(2400/175 lpi). our rip is fuji( adobe latest appe rip) and ctp fuji violet.the funny thing is we are able to match dot to dot from thermal ctp but we couldn't able to match with printed sheet. i think ink reception is high for Violet, if we reduce the increased dot in violet gradiation size(area) is reducing by 30%. pl guide me