D is dead, kind of
D is dead, kind of
Density is still used by the press, built in or hand held device to control the press.
To print ISO standard you need to print the right colour (Lab) in your primaries (CMYK), as was mentioned here.
To find the right densities for the press operator you need to either use an advanced hand held "spectro/densitometer" or a spectro with computer and application where you can compare the measured colour with the standard you want.
There are several solutions for this on the market. Please come back to me if you want names and brands (I avoid this here since it can be concidered marketing and also since the graphic biz is very emotional about brands).
Once you have the tools needed you can start. If your situation is "normal" (as in what ISO specify) regarding plates, screen, press condition and paper classification then you can just go ahead.
If you use a exotic setup as in special screen etc you might want to start with by printing a print contrast check, dot gain check etc. (I can elaborate if you want).
Note: when you measure density normally most instruments have POL filter. That is not the case once you measure spectrally (Lab).
Therefore you need to let the print dry before you measure spectrally.
- Print and check Lab, when you are close note (write down) the wet densities in press with densitometer used by press operator.
- Wait about 15 min for coated stock and some minutes for uncoated stock before spectral check.
The dry back for CMY is normally about 3%. About 10% for K. (% relative to your density).
Once you have scored the primaries spectrally you have can tell the press operator what densities he or she need to use for each paper stock.
Note: many modern press pulpets have spectral measurement today.
Interesting observation in Sweden (and other countries):
Printing competition "Best Print 2011".
The goal for this competition is to print the colour your client give you: best possible reproduction within the ISO standard. How you reach this is your problem.
One print shop (amoing many) does not put curves in the rip etc to try to match the ISO standard for dot gain, gray balance etc.
They simply print the right primaries and secondaries (C, M, Y, K and CM, MY, CY).
Then they make a profile measurement. Feed it into their CMS System and convert the job.
This way you get an exact match with whatever the client give you in terms of colour.
This they did as usual.
They won on all points. Perfect reproduction.
But.
The "dot gain" was not god. Dot gain measured with some densitometer with Murray Davies principles. Not sure why it went wrong here. Could be because it was FM screen perhaps. *
So they did not win. Second place...
Wierd. ISO define colour. Colour is reproduced. Density we do no longer care about. Why on earth shall we then refer to dot gain?
Does the client care what dot gain you have when the colour is perfect?
One foot in the new world and one in the old. It is time the offset/gravure/flexo industry decide what the press shall print rather then kneeling down by the press and let it decide for you.
What dot gain do you have in your Indigo?
http://printplanet.com/forums/images/smilies/smile.gif
*/ If you have a perfect proof. You also have a perfect match in press. Colour is within dE 2. Then take you densitometer and check the density and the dot gain.
It does not work! It depends on pigments etc.
So stop the density and dot gain humbug if you ask me.
Can still be used in press though. Press control. Nothing else.
Good luck.
Best regards
Bohlin
