Compensating for Dot Gain

[LoganBlade]

i just did my curve on my delta.
step one linerize ctp out put.
then ran scales 2 3 5 10 25 30 40 50 60 70 75 80 90 95 97 99 100 and out put plates for press run.
had pressman run to standard density on cymk colors.
read my dot gains.
set my goal dot gain in rip. k 68% cmy 64%
entered the measured values from press run and rip made calculations for proper dot.
a tweek here and there but that is it.

Haliquin no idea

[DigitalCrapShoveler]

One day we were messing with this and couldn't remember which way the curves went. Finally somebody was brilliant enough to say, "you know if it's wrong we can always go back the other way."


And Shoveler, may I be the first to offer an assessment of your higher-ups for compensating for dot gain by changing photoshop files? I mean I understand if your total ink is all wrong, but to change the curves in the individual pieces of art instead of adjusting the output device to compensate for the device being out of synch can charitably be called "less than inspired."

And I'd bet I'm a lot more charitable than you were in this situation.  :wink:


Roxy: welcome, and good luck with this stuff. We're here to help and can provide references.  :grin:

Gut, I hear you and I have had the privilege in the past of having a competent manager. One who understood CIP data and the importance of TIC and Dot Gain. My manager now is a very "standardized" individual in a custom offset shop. He believes in uniformity, because operators are too stupid to modify head trim or lip. He refuses to learn anything new, and has absolutely no idea how to operate any mainstream desktop apps, besides Acrobat. He is a micro-manager, and reminds me of Bill Lumburg from Office Space. But, he is the man, so I do what I am told. It took me a year to get him to start running 133 on offset, because it was killing our Press Guys. Point I am making is, there a progressive Prepress guys, and Archaic Prepress guys, my manager is obviously the latter, and as long as he is in charge, he makes the decisions. He blankets the acts of the department as whole, and because of that the higher ups are fooled by his menagerie. As long as the work gets out on time, NOTHING else matters. I do the majority of the work, about 50-53% on average, however the sausage sitting across from me does about 20%. See what I mean. I get no recognition, and my opinion matters little, even though I have been doing this longer than anyone else, except the manager. I just try to slip in as much as I can to help the other departments, under the radar of course. One of those things happen to be hand applied curves.

[Roxy]

Hi Digital,

When you refer to CIP data, Is that a tiff file that is exported from the workflow system to the press control system to make for quicker setting of the ink keys on press? TIC, thats the "total ink coverage" right...or as we call it TAC - Total area coverage...same thing? We have a TAC of 240% - Just curious, how does one come to that conclusion...It was 240% when I got here...

Roxy

[DigitalCrapShoveler]

Hi Digital,

When you refer to CIP data, Is that a tiff file that is exported from the workflow system to the press control system to make for quicker setting of the ink keys on press? TIC, thats the "total ink coverage" right...or as we call it TAC - Total area coverage...same thing? We have a TAC of 240% - Just curious, how does one come to that conclusion...It was 240% when I got here...

Roxy

Yes, CIP Data is the data shared with the press for more efficient ink control. TIC, an TAC are essentially the same thing. One being Total Area Coverage, And the other being Total Ink Coverage. Total Area Coverage indicates the areas on a press-sheet where ink overlaps and the density it reads. Total Ink Coverage is the total combination of inks overlapping once the file has been flattened.

[Roxy]

What exactly does linearize plate mean? I'm assuming it means to produce a plate without any adjustments made on RIP. In essence, 50% on screen images at 50% on plate...that right?

[DigitalCrapShoveler]

What exactly does linearize plate mean? I'm assuming it means to produce a plate without any adjustments made on RIP. In essence, 50% on screen images at 50% on plate...that right?

That is correct. Sometimes however, the values you measure will be a point or two off, this is acceptable. When you imput your values for compensation curves, you can fix them at that point.

[Roxy]

Thanks Dig,

So when compensating for press gain, you would also take into account whatever is off on the linearization as well and factor that into compensation curves as well...

[DigitalCrapShoveler]

Thanks Dig,

So when compensating for press gain, you would also take into account whatever is off on the linearization as well and factor that into compensation curves as well...

Okay, let's say for illustration purposes you have 11 points in your linear curve. 1-10-20-30-40-50-60-70-80-90-100. Let's say you are reading them like this: 2-11-20-32-40-51-61-71-80-90-99. When imputing your calibration curve for linerazation you would fill in the correct numbers. Run a test to make sure the numbers are coming out like you want, then add your bump for hilights, and take away from your shadows for dot gain compensation.

[Gutnbg]

pssst...

... since you're not hearing any dissenting views, you can assume the man knows what he's talking about.

(He does. He really does. Two thumbs up, Shoveler.)

[DigitalCrapShoveler]

pssst...

... since you're not hearing any dissenting views, you can assume the man knows what he's talking about.

(He does. He really does. Two thumbs up, Shoveler.)

I appreciate the compliment Gut... Thanks.

[Roxy]

Okay...

Something is amiss here. More guidance from the experts please.
Just did a test where we created a plate with a 50 cyan patch and ripped using the compenation method we talked of earlier...that being putting a 75% ...(for the record - 75% is what we read off of the printed paper produced from a linear plate) in the 50% field on the RIP. Before putting this plate on press, I read the plate and it gave us a reading of 38% in the 50% patch so I thought we'd be in good shape...38% on the plate...should hit about 50% by the time the dot grows...anyways, after printing this, the reading of that 50% patch gave us a 72%...WTF? This is obviously something at the press level thats f'd...right?...no way can my 38% patch/plate would grow to produce a 72%...

Any ideas? :cry: :cry: :cry:

[DigitalCrapShoveler]

Sounds pretty fishy to me. 38% going to 72%? Thats like 90% dot gain! Could be press, but make sure you check everything on your end, because not only do you have to show the Pressman the problem, but you're going to have to prove it to him. From the numbers you give prior to the printing, everything sounds good.

Have you fingerprinted your presses yet? Or are you just in the first initial stages of setting up?

[Roxy]

Yeah, the 38% on plate was perfect - it all went to hell after that. How would one go about fingerprinting the presses? I've heard about it but never actually researched the process...

[Joe]

All you can do is make the plates read what you want. It's up to the press after that. Originally your 75% read a 90% so you had 15% dot gain in the 3/4 tones which should mean your 50% was probably reading about 62% - 63%. No way you made the 50% become a 38% on plate and the press ran it up to 72% unless there are press shenanigans going on. Fingerprinting a press basically means taking the solid densities up to the proper values and calibrating all of your other equipment to match it. I think you've done everything correctly. Just my 2 cents worth here.

[LoganBlade]

My Answer is the same as joe. It is what it is. You will not be printing a 50% dot on paper it should be between 68% to 70% on the black and 64% to 65% on the CYM. if you entered 75% in your reading change it to 78. your printed sheet should read like the following.

K-50% = 68%
CYM-50% = 64%

basically if you do this process for each press and for coated and uncoated paper you should end up with minimum of 2 ques per press. the 75% you read on one press might read 69 on another depending on press operator time of day, did your pressman have his coffee or not. You can only control your end if the pressroom forman/supervisor manages his workers to follow a standard.

good luck.

ThankGod i manage curves in prepress and the pressman. It can be tough if you don't haqve good cooperation