it seems that dot gain on offset in a longggggggg and debatable issue for centuries, but i find it comfortable to apply on me rater than on machine , jokes apart, i have a brand new sm74, i have done the curve setting on ctp with my guru mr dieter kirchner, seems to me that things are going alright, my standard densities have changed i m running black between 1.95-2.10 but still my dot gain of 50 is coming not more than 65 which is fair, my point is little different, what should be the ideal dotgain for good contrast and good printing , ie if i am using the other curve of uncoated profile which we have compensated i am getting the dotgain of not more thn 10% on 50 ie 50 is coming 60, is it good or no ? please advice,
The correct dot gain is the one you can hold all day
Hello Arshad.
The correct dot gain isn't so much an ideal percentage (though if you're regularly getting 10% dot gain at midtones, you're doing pretty good), but a target that you can hit consistently and reliably account for. If you <i>know</i> that you can hit 10% dot gain for a given press and paper stock all day, every day, you can account for that limitation in prepress to "net out" your original screen percentages. You'll be doing all right.
The latest versions of Adobe Creative Suite graphic applications and QuarkXPress page layout software allow you to dial in color settings to account for press limitations, including dot gain compensation curves. With predictable dot gain compensation, ideally, you should be seeing a 50% screen on press where you want to print 50%. The only place you should see measurable "dot gain" in your print jobs would be in the calibration bars outside the job's trim area.
Did you MEASURE the mechanical dot area on plate? By what means?
Likewise for the printed piece.
JRHMobile lays out a good plan for the most part, but "you should be seeing a 50% screen on press where you want to print 50%. " needs clarification.
If it LOOKS like a 50% dot on the printed sheet, as seen under high magnification or on a good dotmeter, then it will MEASURE substantially more due to optical dotgain alone, and THEN add your physical dot gain due to ink.
MUCH time and money has been wasted due to misguided application of electronic prepress and CTP curves. Don't fall into an easily avoided trap.
Dot Gains in the Mid-tones CM&Y should generally show no more variance than ~ 3% from top to bottom except for K - which is always higher. So a CMY range +/- 3% means if you are printing a 50% M @ 65%, Y should then be not less than 62% (with C being in the middle) theoretically making and holding on press, best subtractive color balance.
Contrast is a Ratio # between Densities and Dot Gains and useful to express how to best make house Density standards and for knowing best high image reproduction abilities on your presses varying stocks, blankets, inks, etc. The higher the contrast # the better your print.
Measuring both Density and Dot Gain in one step is Contrast and is intuitively useful. The higher the Contrast # the better your print as the press is laying down the "optimum ink thickness" (not too much and not too little) along with the optimum Dot Gains.
Stated one other way: How much ink can I lay down before I begin to plug up in my shadow tones? Keeping this open is "high print contrast" where images jump of the sheet.
So Densities and Dot Gains are relative numbers helping to guide faster press make-readies, maintain good press color balance and to produce higher Contrast prints that "Snap" "Pop" or "Jump" off the sheet.
Sincerely,
Greg Imhoff
Originally Posted by Arshad
it seems that dot gain on offset in a longggggggg and debatable issue for centuries, but i find it comfortable to apply on me rater than on machine , jokes apart, i have a brand new sm74, i have done the curve setting on ctp with my guru mr dieter kirchner, seems to me that things are going alright, my standard densities have changed i m running black between 1.95-2.10 but still my dot gain of 50 is coming not more than 65 which is fair, my point is little different, what should be the ideal dotgain for good contrast and good printing , ie if i am using the other curve of uncoated profile which we have compensated i am getting the dotgain of not more thn 10% on 50 ie 50 is coming 60, is it good or no ? please advice,
Gentlemen, a 50% plate dot that prints a 60% dot is a gain of 20% i.e. 60/50 = 1.2 or 120% A GAIN OF 20%
Problem here is dot gain is often talked about in terms of percentages. This should be thought of as units. when a 50% plate dot measures 60% on the printed sheet, that an increase of 10 units (more often referred to as 10% gain). Though your math is correct, this isn't what is intended to be communicated.
Kinda surprised that there's still such discussions of the basics of dot gain. If only there were some guru out there who blogged about such topics in an easy to understand manner.
The conversion from RGB determines the 'dot gain' of the C-M-Y-K file. The default in Photoshop is around 20%, therefore a 50% patch should read 70% at press. Certainly you can print sharper (10%) or heavier (24%) but the seps and the Pantone book (screen builds) are made with 20% midtone gain. If you separated for newsprint it's 30% gain. The new G7 curves print with 15-17% gain and appear sharper or cleaner in print. You can separate for uncoated (more gain) but no one ever does. That's why you need plate curves for uncoated as well.
Any questions please call.
So, if you printed with 24% gain you would print 'darker' than the standard.
Dan Remaley (Google Me)
412.889.7643
Gentlemen, a 50% plate dot that prints a 60% dot is a gain of 20% i.e. 60/50 = 1.2 or 120% A GAIN OF 20% This seems excessive. How was it measured? Are the impression settings correct, blanket hardness? Even on uncoated stock the repro curves should give better results.
You need to run the press to an ISO standard and measure the gain for that exact stock - press combination.
Just for the record - that is completely wrong information.
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Dot gain
, jokes apart, i have a brand new sm74, i have done the curve setting on ctp with my guru mr dieter kirchner, seems to me that things are going alright, my standard densities have changed i m running black between 1.95-2.10 but still my dot gain of 50 is coming not more than 65 which is fair, my point is little different, what should be the ideal dotgain for good contrast and good printing , ie if i am using the other curve of uncoated profile which we have compensated i am getting the dotgain of not more thn 10% on 50 ie 50 is coming 60, is it good or no ? please advice,
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Originally Posted by Arshad
