Dot Gain

[PeterArnel]

I really need help here - there is a huge debate going on as to whether printers compensates for the dot gain he gets on his press by reducing the dot on his CTP plate or whether he runs a linear plate - which is 50% digital dot = 50% on the plate and accepts the dot gain
If printers are lurking around or any one can ask their printer what they do I would appreciate it
Peter

[annc]

Originally Posted by PeterArnel

If printers are lurking around or any one can ask their printer what they do I would appreciate it

Oh dear, Peter, I do hope some more printers jump in here. I just do up my files and leave all that stuff to the printer!

[don Arnoldy]

Originally Posted by PeterArnel

there is a huge debate going on...

IANAP, why is this a debate? if you *can* compensate for dot gain, why wouldn't you?

--don

[PeterArnel]

The debate or research is that there is no standard for what the doit gain should be - It would be good if 50% digital dot = 50% on the paper - but this is not practical as we would never match previous work.
Some of us believe that there has to be a standard based around 50% = 64% CMY and 67% on the black -Its a real problem for clients who get work printed at different printers as the colours never match
Peter

[Michael Rowley]

Peter:

there has to be a standard based around 50% = 64% CMY and 67% on the black

Since paper varies so much, and, of course, the printing method, isn't it a case of 'Suck it and see'?

[ktinkel]

Originally Posted by PeterArnel

The debate or research is that there is no standard for what the doit gain should be …

This strikes me as a problem of new printing technologies. We used to be told that dot gain was an increase in dot size that could be blamed on (er, was attributable to) errors (er, variations) in contacting, making the plate, or mechanical differences with presses. Perhaps even differences in printing stocks.

Then, when imagesetters became a standard, it was sometimes blamed on exposure, emulsion, or whatever variations.

It never occured to me that dot gain might be a standardizable issue. In fact, as a designer (at least during the first 25 or 30 of the past 40 years), I was always told not to worry about it, that this was in the realm of printer expertise and related to the printer’s equipment and his experience with it.

Has all this changed somehow? Or do they know something today they didn’t know about dot gain 10, 20, 30, or 40 years ago?

I also remember that printers used to use textbook mathematical equations to determine the gain for a particular job. Are these no longer useful?

[don Arnoldy]

Originally Posted by ktinkel

We used to be told that dot gain was an increase in dot size that could be blamed on (er, was attributable to) errors (er, variations) in contacting, making the plate, or mechanical differences with presses. Perhaps even differences in printing stocks.

Dot gain is chiefly influenced by the viscosity of the ink, and the absorbancy of the paper. Chemical drying accellerators and in-line driers can reduce it too. Variations in the film/platemaking process also factored in.

For any press/paper combination, dot gain should be calculable--empirically, if nothing else.

I would be an unhappy camper (customer) if my 50% tint turned into a 65 - 67% tint.

[ktinkel]

Originally Posted by don Arnoldy

Dot gain is chiefly influenced by the viscosity of the ink, and the absorbancy of the paper. Chemical drying accellerators and in-line driers can reduce it too. Variations in the film/platemaking process also factored in.

For any press/paper combination, dot gain should be calculable--empirically, if nothing else.

I would be an unhappy camper (customer) if my 50% tint turned into a 65 - 67% tint.

Sure. But it does sound as if all the variables are within the printer’s control, and since they do not all have the same equipment, supplies, or practices, hard to standardize. No?

[ktinkel]

Originally Posted by PeterArnel

The debate or research is that there is no standard for what the doit gain should be…

Continuing from my earlier message, I fell upon a copy of the 1992 edition of the Graphic Arts Encyclopedia (I can never find any book when I need it, but this literally almost fell off the shelf).

It more or less confirms my earlier thoughts, but also refers to the equations by which printers calculate dot gain in order to compensate for it: One is the Murray-Davis equation, the other Yule-Neilsen (which is a modification of the first).

Another thought: I had always heard that English printers used positive transparencies rather than negs as we in the States do. If so, couldn’t that also affect dot gain?

[PeterArnel]

Dot gain in the past was based on tests that were carried out and agreed world wide - targets were set for either negaitive film or positive film. The difference gain/loss for film was caused by the film being printed down onto the plate - with pos film we got dot loss about 2 - 3 % and with neg film u got dot gain 2 - 3 % so the difference could be as much 6%. I am sure you know that the gain is always expressed as a % of 100 solid ie 10% on 50% would equal 60%- THats why US printed work always looks darker in the mid and three quarter tones. CTP has taken these gains away - so Europe now has more dot gain - and the ISOcoated targets have set TVI dot gain curve to reduce the gain. I am not sure whther the US are adding the dot size to increase gain.
Its a real Beggars muddle
Peter