Dot Gain

[richie4400]

Hi There

Can someone please confirm my understanding of dot gain is correct.
We are currently printing to Fogra 45 standards which means a 40% CMY patch on the artwork should measure 56% (16% Dot Gain) on the printed sheet and a 80% CMY patch on the artwork should measure 91% (11% Dot Gain) on the printed sheet.

The reason I ask this is I had a visit from a "Colour Expert" and he said that a 40% patch on the artwork should print as 40% on the printed sheet. I see this as printing "linear" and not to any standard (ie Fogra).

Thanks in advance.

[Munsell]

That colour expert should have his badge taken away. You really don't want a press printing linear. Dot gain is normal and expected. You should work with it, not against it.

The way I approach it in our plant is as a process control tool. I don't shoot for any specific dot gain value. When I calibrate the press, I record the dot gain. As long as its something normal, I set that as the "standard". Then, it can be a tool to see if something is wrong with the press, or print quality. As long as I'm experiencing generally the same dot gain, I know certain aspects of the press are functioning properly.

[Lukas Engqvist]

Never trust an expert By CMY you mean a C, M or Y I hope. But you seem to be able to read the standard ok.

[richie4400]

Thanks for your comments.

I agree you have to be careful when you put yourself out there as an "Expert"

[richie4400]

Sorry Lukas, I did not answer your question.
Yes, when I say CMY I refer to Cyan, Magenta and Yelo.

Many Thanks

[Lukas Engqvist]

Oh and make sure the sheet is dry when you measure dot gain, was too quick once and measured uncoated while it was still bleeding

[rich apollo]

Oh and make sure the sheet is dry when you measure dot gain, was too quick once and measured uncoated while it was still bleeding

Eek! That can be rough on the lens.

The "expert" in question is preaching against my experience. I set up a linear scenario like he describes...once. I learned that I like dot gain.

[JudP]

Hi All, so in regards to this dot gain question...I definitely agree with what Munsell says that this is a process control tool. I am currently implementing a major color management upgrade in my plant and as the Pressroom Manager I wanted to get some advice on what to do if my dot gain shifts. In doing my standardization runs, I do record my dot gain however this past week I've noticed that my dot gain on K, C and M have all decreased about 7% on my Goss Sunday 2000 (38" web).

Any advice on what to check for? I know the obvious, roller stripes, squeeze settings, etc but I can't think with anything that would cause such a drastic shift (or maybe this isn't so drastic????)

[gordo]

Hi All, so in regards to this dot gain question...I definitely agree with what Munsell says that this is a process control tool. I am currently implementing a major color management upgrade in my plant and as the Pressroom Manager I wanted to get some advice on what to do if my dot gain shifts. In doing my standardization runs, I do record my dot gain however this past week I've noticed that my dot gain on K, C and M have all decreased about 7% on my Goss Sunday 2000 (38" web).

Any advice on what to check for? I know the obvious, roller stripes, squeeze settings, etc but I can't think with anything that would cause such a drastic shift (or maybe this isn't so drastic????)

I'm not so sure that dot gain is a process control tool in the same way that it was in the days of film. Today, the dot gain characteristic curve is more of a target for tone reproduction in the press work. Because dot gain is tied to solid ink density, as SIDs naturally vary through the run, so will dot gains. There's a video on my blog that shows this quite clearly - click here: Quality In Print: On-press stability and consistency

Are you doing your standardization runs differently than how you run the press normally?

best, gordo

[JudP]

Thanks Gordo,

Much to my chagrin I only recently came across your site and have been reading all of your articles so well done on the good work and please, from all of us, keep it up.

I do see what your saying and this is what I thought too before I started researching this more and a lot of people say that they are now using this as a process control tool.

I want to start using this to target press runs to as well and will check out your video.

Our standardization runs are all done on the same stocks, same ink manufacturer, line screen, etc.

Jud