ISO Ink density

[pacificiam]

Wat are the ISO standerd ink densities for Coated, Uncoated, Matt and Duplex?
plzz Mention Iso Ref. No

Thanx

[gebalazs]

Hi!

ISO standard for offset printing (12647-2) don't use ink densities as target values anymore but Lab targets. If you have the right paper and ink do a test printing and see at what densities you can reach the required Lab values.
If you don't want to go that way, I share the standard from 1996 with you. It still shows the densities.
The document is English / Hungarian.
http://dl.dropbox.com/u/2197811/Dens...in%20chart.pdf

[Chief_1975]

ISO doesn't specify ink density only LAB target values for solids, it up to printer to determine the correct density to hit the target values in ISO.

[Johu]

You could also ask for the ideal densities from your ink manufacturer.

[joe pasky]

You can establish your shop densities this way for a given ink set:

Load the ISO reference values for each process color into the memory of your spectro. Set up the spectro so that when you measure the solid patches, it reports back the dE(ab) from this standard.

Start printing with the IFT of each ink fairly low such that the dE is greater than 5.0. (the ISO tolerance for solid ink is 5.0 dE(ab).

Gradually Increase the IFT and take note of the DENSITY when the dE becomes 5.0.

Continue to increase the IFT. As you do this, the dE should remain under 5.0 for some range of increasing IFT. When the dE starts to exceed 5.0 again, note the DENSITY at this IFT.

This RANGE of densities where the L*a*b* of your ink-set is less than 5.0, become your shop densities.

The 'correct' ISO density is anyplace within that range for each color. Use that tolerance to adjust the IFT of each printing ink to achieve gray balance. Gray balance is your FIRST priority.

If the correct tone and balance cannot be achieved when your densities are within this range, your CtP curves must be adjusted. (use the G7 method).

The ISO L*a*b* tolerances will give you a range of densities within which you can work and still be ISO compliant. Note that some process inks will have a wider tolerance range than others. Wider is better.

Joseph J. Pasky
Shenzhen, China

[danremaley]

Wat are the ISO standerd ink densities for Coated, Uncoated, Matt and Duplex?
plzz Mention Iso Ref. No

Thanx

I have a very simple way of matching and measuring based on Density and TVI, coated and uncoated. . .call me. Uncoated is .95Y 1.00C 1.12M 1.25K these are dry densities, tonality (TVI) is the same as coated.
Dan Remaley
412.889.7643

[Achtung | Spitfire]

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

[Erik Nikkanen]

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.

So stop the density and dot gain humbug if you ask me.
Can still be used in press though. Press control. Nothing else.

Bohlin

I totally agree with you on these points Bohlin.

The printing industry does so many things based on old thinking. I the future, it will look down right stupid what is done now. We are in a transition period without much leadership to the future.

[gordo]

Since the major function of a press is to lay down a film of ink, press operators use density measurements as an indirect way of measuring the ink film thickness.

Can someone explain how you derive ink film thickness from CIE Lab values?

thx, gordon p

[Erik Nikkanen]

Since the major function of a press is to lay down a film of ink, press operators use density measurements as an indirect way of measuring the ink film thickness.

Can someone explain how you derive ink film thickness from CIE Lab values?

thx, gordon p

Of course it is not really needed. The press function has nothing to do with colour as you implied. Consistent colour is just a by product of consistent management of ink film etc.

If one wanted to use CIE Lab values to monitor ink film, I guess you could just use the L value. When it goes up then you are probably running with thinner ink film. There is nothing sacred about Density values. It is just convenient due to the choise of filters and the log scaling.

Dot gain and density have no direct relationship with colour as was commented on earlier.