Dot gain compensation

[2shoff]

Our shop recently did a press/CTP calibration which led to the discovery of above normal dot gain with our magenta and yellow. Now that our CTP has the proper calibration curve it's a big improvement over the very red-heavy results we had been getting. Unfortunately, our problem wasn't totally solved because our CTP uses poly plates and they just aren't holding screens as well as when we go to negs and metal plates. We are a small shop and have to have another local printshop output our negs for us, then we strip it up and burn plates. So, obviously, the calibration done with our CTP doesn't help us when we need to go to metal plates for certain jobs. Would a possible solution be to make a custom color profile? If so, is this my best/only option? What would be the most cost-effective way to create the custom profile?
Any thoughts/recommendations would be appreciated.

Thanks!

 

[Lukas Engqvist]

Re: Dot gain compensation

Sounds strange to have an abnormal dotgain in two of the colours. Sounds like the dotgain problem is in your press and not your CTP. I would check that the press is healthy and that you have the right target density.
If is fine to compensate for that defect however, and curves is good way to do it. If you need to apply the transfer curves you can create an ICC profile or have a device link profile (preffered for CMYK to CMYK) So that you convert to a CMYK file with the compensation for your dot gain.
There are server soloutions that work by hotfolders so you put the file in one and it comes out compensated in the other. If you look at the Ink Limit discussions you will find suggestions, the standalone solutions I can think of are Alwan colour, GMG colurserver and TGLC's PerfX. It may be more expensive than you were intending, maybe others have more suggestions.

 

[meddington]

Re: Dot gain compensation

>Would a possible solution be to make a custom color profile?

Profiling is a possible solution, however undergoing a calibration process via curves (tvi or G7) is probably a bit easier to perform and implement into the workflow. Both calibrating via curves (TVI or G7 methodology) or profiling requires going to press with the proper target elements for measurement imaged on the plate type in question. Profiling may have more accurate results colorimetrically, but is a snapshot of the state of the press. If the press isn't stable, the profile has limited value. Profiling can also require more significant changes to the workflow to implement the profile...where and how do you perform the conversion (see Lukas's post). Calibrating via curves can reduce or eliminate the need for custom profiling, and is often recommended prior to profiling. My recommendation would be to undergo a calibration via curves first, evaluating the results, and then proceed with profiling should it be necessary (while determining how to best implement into your workflow). You could either target the gains from your CTP process with your conventional process, or target them both to a common standard (ISO 12647-2 or via G7 method). This would basically involve imaging linear plates (film in this case), determining the needed compensation, and asking your film supplier to apply the compensation to the film you receive. Again though, as Lukas stated, your press needs to be healthy and stable.