Dot gain

[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,

regards
arshad.

 

[Cornishpastythighs]

Your getting 15% dot gain and running an ink density of 2.10. I can only say Wow, I have never seen that before!!!

 

[Arshad]

dot gain

dot gain

well thanks for that. i am using a high gamut black..

 

[jrhmobile]

The correct dot gain is the one you can hold all day

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.

 

[ljgoldberg]

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.

 

[Greg Imhoff]

TVI Dot Gains and Print Contrast

TVI Dot Gains and Print Contrast

Hi Arshad on Dot Gain Balance and Contrast:

1. 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.
   
2. 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

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,

regards
arshad.

 

[meddington]

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.

 

[meddington]

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.

Oh yeah...thanks Gordo!
Quality In Print: Dot Gain/TVI (Tone Value Increase) - part 1 of 4

 

[danremaley]

dot gain

dot gain

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

 

[gordo]

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.

50% dot plus 20% dot gain/TVI = 70% tone. End of.

best, gordo

 

[Arshad]

dear all,

talking about the basic thought process of dotgain is 50 should come 63-64 thats the parameter world follows. i am more concerned abt the sharpness and contrast, according to me , maximum ink and minimum water with dotarea covering upto 64 , i think the target of c.m.y will achieve and black will have 3 or 4 % more , i think i am achieving that, with good midtones and shadows, without loosing details from the image,

Yesterday evening when we were doing calibration for FM screening , My densitometer was showing different values at different angles and different times, I dont understand wat was going on, may be my densitometer is not capable of reading FM 20 micron, please advice,

regards
arshad.

 

[gordo]

My densitometer was showing different values at different angles and different times, I dont understand wat was going on, may be my densitometer is not capable of reading FM 20 micron, please advice.

Are you measuring the plate or the press sheet?

Densitometers don't know anything about halftone screens. So, the halftone screen makes no difference when using a densitometer.

best, gordo

 

[Akila]

Hi iam Using ptr 8300n-s Ctp & my work flow is trueflow se.
i just want to know what is the best dot shape for ctp & plate

tnx.

 

[Mike Strickler]

Dot Gain

Dot Gain

I know this is obvious to many here, but it's worth pointing out to some: When you are judging dot gain as normal, high, or low, be sure that no plate curves have been applied. Measured "dot gain" is the sum of your press gain and whatever curves have been applied. Your densitometer only shows the net result.

 

[Greg Imhoff]

Dots & Spots are not the same in or on dot gains

Dots & Spots are not the same in or on dot gains

Dot gain is a handy guide - a on press tool to faithfully control image reproduction. Dot Gains are derived from logarithmic Density readings meaning the less light seen = the higher density and is calculated via algebraic equations automatically.

Reporting of Dot Gain measurements (eg: 10 %) are best if including the LPI or screened values too. A 10% gain in a 50% target has more "dot growth" than say a 10% gain in a 25%. The same applies for screen rulings too as a 200 LPI is a finer screen than a 100 LPI. The same is true if printing FM and Hybrid so to best improve prints report "net dot gains" along with in % tint or on screening values too.

We know all presses print differently and we also know dots n spots are not the same so - to improve your image it is simply best to state your net dot gains, along with the screens read. Sincerely, Greg Imhoff

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.

 

[gordo]

Hi iam Using ptr 8300n-s Ctp & my work flow is trueflow se.
i just want to know what is the best dot shape for ctp & plate

tnx.

If you are using an AM/XM screen (rather than FM) then the best shape is "Round"

See here for why: Quality In Print: AM Screening Dot Shapes

best, gordo

 

[Greg Imhoff]

If AM or FM press dot gain will be dot gain.

Generally speaking FM prints sharper (with less ink and or gain per se) so, if printing 20 micron and you are losing Contrast (aka plugging up in the Shadows) the problem is in Plating. This is not correctly curve calibrated to compensate for the spots coming from the RIP, to the Plate, to the Press. Your images are not balanced to meet the physical press challenge. Calibrate your plates to match your print curve.

 

[meddington]

Hi Greg,

Generally speaking FM prints sharper (with less ink and or gain per se)

Hmmm. I agree that when the some tonality is being measured between AM and FM, there is generally less ink usage with FM, but I disagree that FM is inherently "sharper" with less gain than AM. In fact, my experience is that cutback curves are necessary to meet Gracol/SWOP/ISO aim points, indicating that there is more gain with FM than AM.

 

[gordo]

Hi Greg,
Hmmm. I agree that when the some tonality is being measured between AM and FM, there is generally less ink usage with FM, but I disagree that FM is inherently "sharper" with less gain than AM. In fact, my experience is that cutback curves are necessary to meet Gracol/SWOP/ISO aim points, indicating that there is more gain with FM than AM.

Correct.

If AM or FM press dot gain will be dot gain.

Correct - but the question was about dot shapes not dot gain, which is why I made the clarification.

best, gordo

 

[Greg Imhoff]

Hi Gordo and you are correct. In fact after posting thought about how in FM the "irregular" shape of a FM shadow vs. the regular dot shape of AM actually creates in FM more "surface area" to gain.

Conversely FM highlights feature smaller spots with a higher frequency when compared to AM screened highlights so ...

I then comforted my self on post "after thoughts" with a belief of "lets just keep the dot gain topic simple" - only to realize that goal is surely fleeting. Knew someone would call me out and thank you for keeping it real. Sincerely, Greg

Correct.



Correct - but the question was about dot shapes not dot gain, which is why I made the clarification.

best, gordo