Problem with fine raster

[marlowe70]

Hello
We have PTR 8300 E and Trueflow SE Rite. After expose is on the plate raster 0,3%.
We have problem with this in print. (For example: image background is 0,3%C+0,4%M+0,5%Y+0,4%K on the computer screen I dont see this but in the print is gray background).
Can I set stronger exposure? I need remove raster less than 1%.
Sorry for my bad english.

[Lukas Engqvist]

the colour you describe would be gray, possibly a warm gray, but you are asking for precision that is hard to measure.
Can you see the raster data? Some systems will clip anything below a certain percentage (to avoid boxing with dirty white cutout photos).

Also remember if you have 8 bits, your steps are at the most 0.4% wich means mathematically you are probably sending 0.4% CMY & K so asking for difference of 0.1% / colour is just too much.

[marlowe70]

Thank you for your answer.
But this not Rip problem. In Rip prewiew I see this raster. Its ok.
But I need remove this raster from plates after exposure.
For specification: I have bad file from customer with light image background ( I wrote gray background in print but of course when is image background 0,5%M+0,6Y is red background in print), and I need remove this fine raster during exposure. It is possible?
I think its not Rip problem but exposure problem. I need change exposure strong or exposure time.
I hope you will understand.

[Lukas Engqvist]

In many rips there is the option to clip low percentages. Unintentional fine raster is usually the result of poor colour management or burning out backgrount to "almost" white.

In your rip you can someti´mes create a TVI curve where you clip all below 1% to white. But the result will be that you get an abrupt edge to soft shadows. Better would be to open the files in photoshop and adjust the levels.

Really the problem is that in old school one would want to leave a stray percent in highlights to preserve details. but if you are cutting out to white then white needs to be white and not a small percentage. The small percentage tone was for when you had images in boxes or cut them out using clipping paths.

[ansoft]

Just over develop this plate!

[maxon]

Would be probably safer to slightly adjust the rip linearization /TVI. Even if soft shadows will be a bit affected it won't be that dramatic bearing in mind that extreme highlights will wear out in print anyway. Raster under 2 percent is not something easy to control in most cases.