Why should I print with Dot Gain?

[kewlbigdan]

I am now entrenched in the G7 system. So I got that.
But remembering 15 years ago I fingerprinted a print company to print linear, in other words my curves compensated for Dot gain so the finished print was 50%=50% etc. (rightly or wrongly)
We printed fantastic stuff with near color accuracy.
So now I am in G7 and our typical dot gains are about 25% in the midtones but we are hitting G7 dead nuts on. But our Account Managers don't like our color not matching the Pantone books. (dont get me started on Sales people).

So just for fun, I created a Compensation curve that took out the Dot gain and we hit colors extremely accurately to the pantone book. But that puts us so far off G7 that you can't even see the NPDC curve with binoculars.

So I know the industry standard is to print to a dot gain, but Why??

I am hoping Gordo or Eric can smack me with some knowledge.

 

[Stephen Marsh]

Food for thought - if you did run a linear setup, how would you handle incoming work that was pre-separated for the GRACoL C1 print condition?


Stephen Marsh

 

[Louis Dery]

About your G7 curves and Pantone book: are you using the Pantone + Color Bridge CMYK builds? If so, that is "normal" you are not getting the expected results. Thos CMYK builds are not made for 25% dot gain but close to 16% and there is no reference profile or specific print conditions (RPC) that comes with the book to help understand those CMYK "simulations".

Louis

 

[meddington]

So I know the industry standard is to print to a dot gain, but Why??

You aren't/weren't really printing without dot gain. An offset press will inherently have dot gain, typically from around 14-20% depending on a variety of factors. You could compensate your plating so that a 50% in the file measure a 50% ink-on-substrate, but that would necessitate a cut back curve to remove the inherent press gain for no real reason other than to pretend dot gain isn't there.

Pantone colors....spots or CMYK builds? Pantone spots aren't typically pushed to match an NPDC.

 

[Louis Dery]

Pantone colors....spots or CMYK builds? Pantone spots aren't typically pushed to match an NPDC.

Hello Mike, I agree with you, BUT when Pantone publish Pantone+ Color Bridge (solid to process) and you could not figure out what is the RPC used for their CMYK build, THEN, how could graphic designer use those CMYK values to print job at NPDC G7 certified printer?

Louis

 

[meddington]

Hello Mike, I agree with you, BUT when Pantone publish Pantone+ Color Bridge (solid to process) and you could not figure out what is the RPC used for their CMYK build, THEN, how could graphic designer use those CMYK values to print job at NPDC G7 certified printer?

Louis

Hi Louis,

A valid point, but I don't put any faith in pre-defined CMYK build for Pantone colors. I would typically generate my own builds based on relevant output conditions.

 

[Louis Dery]

100% agree with you Mike! The new Lab references with Pantone + is the best starting point!
My only concern is about the Pantone+ Color Bridge (CMYK values) that are NOT based on a "known, published" RPC. This is, I think, a problem when graphic designers think that CMYK is the same for every printer and they are going to get the best possible match because it is written in the Pantone book ;-)

Hope Pantone wil some day make the move in the right direction to publish or supply more info about their CMYK builds aside of just saying that their book are printed with international standard specs.

Louis.

 

[Alois Senefelder]

Dot Gain

Dot Gain

kewlbigdan,


Because you have no option - but to control Dot Gain(TVI) via Tone Reproduction Curves.


1) Dot Gain is a inherent part of the Mechanics of Lithographic Printing.

2) The Why ? the Forces of Pressure for a start !


Regards, Alois

 

[gordo]

I am now entrenched in the G7 system. So I got that.
But remembering 15 years ago I fingerprinted a print company to print linear, in other words my curves compensated for Dot gain so the finished print was 50%=50% etc. (rightly or wrongly)
We printed fantastic stuff with near color accuracy.
So now I am in G7 and our typical dot gains are about 25% in the midtones but we are hitting G7 dead nuts on. But our Account Managers don't like our color not matching the Pantone books. (dont get me started on Sales people).

So just for fun, I created a Compensation curve that took out the Dot gain and we hit colors extremely accurately to the pantone book. But that puts us so far off G7 that you can't even see the NPDC curve with binoculars.

So I know the industry standard is to print to a dot gain, but Why??

I am hoping Gordo or Eric can smack me with some knowledge.

So, you've gotten some good answers. My take is that dot gain is not the issue. The issue is the appearance of tones in the presswork.
Back in the steam-powered days before digital, linear bilevel film was the accepted file interchange format for the graphic arts. To bring some order to exchanging film, the convention was that the film would represent tones in a linear fashion. I.e. If an artiste specified a 50% tone in their file then the film would have a 50% halftone (i.e. checkerboard - 50% of the dots were 100% K and 50% of the dots was 0% K) representing that tone.
When that film halftone was exposed to the plate and then the plate was exposed to ink and then transferred to blanket and then paper under pressure it got distorted. Ultimately it grew. That was dot gain. But the practical effect was that when the specifier requested a 50% tone what they got was a 72% tone. That tone appearance became the expectation and eventually the appearance standard. It remains so today.
So, if you want to align your print process to the standard then you align your tone reproduction on press to align to it and accept whatever dot gains that, in your circumstance, results in that alignment.
However, you may, for whatever reason, choose to reproduce requested tones differently. You may choose to reproduce a 50% requested tone as 50% in the presswork. In that case you would be printing to your standard rather than an industry standard. You would then moderate dot gains until you achieved the linear presswork that you've targeted. There will be consequences to choosing that path - but it is certainly your choice.


best, gordo

 

[rich apollo]

Dot gain isn't bad, it just...is.The first time I worked with a CTP system, we immediately set about eliminating dot gain - setting up the system so that a 50% in the file yielded a 50% on the printed sheet. The result looked terrible - hollow, flat, dull.

Dot gain isn't something to be avoided, or eliminated. It just needs to be controlled.

Throw away your Pantone Bridge book. There should be NO pre-baked CMYK equivalents for Pantone colors. Pantone colors are not actually color definitions, but ink formulations. The color is the result of printing said ink formulation under specific conditions.

 

[danremaley]

Dot Gain

Dot Gain

I am now entrenched in the G7 system. So I got that.
But remembering 15 years ago I fingerprinted a print company to print linear, in other words my curves compensated for Dot gain so the finished print was 50%=50% etc. (rightly or wrongly)
We printed fantastic stuff with near color accuracy.
So now I am in G7 and our typical dot gains are about 25% in the midtones but we are hitting G7 dead nuts on. But our Account Managers don't like our color not matching the Pantone books. (dont get me started on Sales people).

So just for fun, I created a Compensation curve that took out the Dot gain and we hit colors extremely accurately to the pantone book. But that puts us so far off G7 that you can't even see the NPDC curve with binoculars.

So I know the industry standard is to print to a dot gain, but Why??

I am hoping Gordo or Eric can smack me with some knowledge.

Here's my take on this issue- the Pantone screen book isn't printed to any standard AND it doesn't have a nice gray color bar to confirm that it's printed correctly, book to book page to page. My old book had some density/dot gain numbers (AVERAGED) that were 'near' SWOP numbers. (Interesting tidbit- remember the old Gracol chart, that had midtone gain for M-20% C-20% Y-18% - That's the gray balance formula - when the M&C gain is the same (regardless of value) and Yello is 2% less you have gray balance - at least at the midtones.) The Pantone books were marked M-20% and C24% so guess what- the Pantone books were "casted 4% towards Cyan - Nice huh?) When CTP hit the market the Creo, Kodak, Fuji went to work 'linearizing' the plates (thinking of film), problem was nobody measured a "good" plate to know what a 50% patch became. I did, on a good plate (6-8 micron on a negative plate) measured 54% - so if you wanted to print and match your film based system you needed to add weight to the plate, throughout the tome scale. I also have all the (Wanted) tonal numbers for a press sheet to match 20% gain AND be in gray balance with ISO inks. If you would like them please contact me. The 20% midtone gain numbers will put you closer to the Pantone screen build books. Hallmark Cards printed with NO GAIN. . .they printed a 50% value in file to measure 50% at press, but they were in a "closed" environment and the designer's worked in that system - couldn't match Pantone. The other 'thing' to remember, is that all Photoshop default settings are 20% also -so it's a pretty safe bet. However, if you separated for 10% gain, proofed for 10% gain, and printed with 10% gain, you print exactly the same as the guy who separates for 30% gain, proofs with 30% gain and prints with 30% gain, I always used this example in my training sessions with design, pre-press, and press.
Dan

 

[gordo]

When CTP hit the market the Creo, Kodak, Fuji went to work 'linearizing' the plates (thinking of film), problem was nobody measured a "good" plate to know what a 50% patch became.

I can't speak about Kodak or Fuji however, Creo did not go to work 'linearizing' the plates nor were they thinking of film in that context. Creo certainly measured plates and knew what a 50% patch became.

gordo

 

[danremaley]

dot gain or LOSS!

dot gain or LOSS!

I can't speak about Kodak or Fuji however, Creo did not go to work 'linearizing' the plates nor were they thinking of film in that context. Creo certainly measured plates and knew what a 50% patch became.

gordo

Creo was the worst! Your right Creo wasn't thinking of film OR the correct value, they were only interested in the correct 'exposure' for their positive plates. EVERY Creo shop that I visited, using positive plates, measured the 50% patch near 45-46%! The poor pressman, with tears in his eyes, was pushing Magenta near 1.80 just to get some color on the sheet! Wish you could have been there Gordo . . . .
Dan

 

[gordo]

Creo was the worst! Your right Creo wasn't thinking of film OR the correct value, they were only interested in the correct 'exposure' for their positive plates. EVERY Creo shop that I visited, using positive plates, measured the 50% patch near 45-46%! The poor pressman, with tears in his eyes, was pushing Magenta near 1.80 just to get some color on the sheet! Wish you could have been there Gordo . . . .
Dan

A field service engineer's job was to calibrate the customer's CtP device hence "they were only interested in the correct 'exposure'". They were not paid to be business advisors regarding the customer's print condition.

Guidance as to how customers could leverage the CtP device and digital workflow to help them identify and achieve their business goals came from the "ViP" ("Value in Print") initiative that I developed at Creo in 1998. ViP published educational brochures, hosted seminars (e.g. at GUA conferences, Drupa and Print, and local PIA events) and did site visits specifically designed to educate customers on matters related to print conditions, standards and specifications, screening,proofing, etc. It also put in place the Professional Services team that was tasked with helping customers to integrate their Creo technologies into a coherent, efficient and effective print production and marketing process.

Whether individual customers took advantage of the resources that Creo offered is another matter.

A shop where, as you put it "The poor pressman, with tears in his eyes, was pushing Magenta near 1.80 just to get some color on the sheet!" sounds like a shop that did not take advantage.

gordo

 

[meddington]

When we had our Creo platesetter installed, the techs verified exposure and left for the day. We output uncompensated plates and went on press with a GATF test form. After measuring the gain, we created a plate compensation curve to boost our dot gains to be more inline with industry specifications. Next day, the techs were back to verify everything was operating, and we were already on press with live work and matching our proofs as good as ever. Never once linearized our plates, just verified exposure. As smooth a transition from film as one could hope for, but we knew we had to compensate for the different technology.

 

[Alois Senefelder]

************

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Gentlemen,

Just my two pennies' worth -- A PDF


Regards, Alois

 

[cosmo]

you need dot gain, if you want the values to read 10/20/30 etc on paper then your print will look washed out and dull, read a bit about TVI, thats basically what all the standards are about.