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/Densitiy and dot gain chart.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]

ISO L*a*b* and density

ISO L*a*b* and density

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]

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

 

[Deleted member 16349]

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

 

[Deleted member 16349]

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.

 

[pacificiam]

I am very thankful to all

So now can u tel me what is the ISO LAB values for CMYK?

If u have more details about it please share

Thank you

 

[Michael Ditchett]

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

I so disagree with this statement. Print Cyan at densities 1.3, 1.6, 2.0 and 2.3.

Cyan at 2.0 is not the same colour as 1.3 although it's the same ink in the trough - and of course this goes for each colour. Multiply this affect across all process colours and you will see a direct relationship between colour and density. Dot gain hasn't even entered the fray yet.

This has a tremendous impact particularly in the packaging industry where the same product is printed in different cities and countries.

 

[Deleted member 16349]

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

I so disagree with this statement. Print Cyan at densities 1.3, 1.6, 2.0 and 2.3.

Cyan at 2.0 is not the same colour as 1.3 although it's the same ink in the trough - and of course this goes for each colour. Multiply this affect across all process colours and you will see a direct relationship between colour and density. Dot gain hasn't even entered the fray yet.

This has a tremendous impact particularly in the packaging industry where the same product is printed in different cities and countries.

Sorry but I have to disagree with your view. The density of two different Magenta printed inks can be the same but the colour does not have to be the same. Matching densities of a proof and a print does not mean that they have the same colour.

 

[gordo]

Before this thread spirals off into the weeds, I would like to see the opinions of people like Achtung | Spitfire on how they measure ink film thickness - or whether it's even a concern to them. AFAIK there isn't a direct conversion from CIELAB, or XYZ, to density since CIELAB and XYZ are based on visual color responses, while densitometers are designed to measure material properties of various systems.

I'm not concerned with color at this point since the press function itself has nothing to do with color. It's purpose is to lay down a film of ink of a certain thickness.

thx, gordon p

 

[Deleted member 16349]

I'm not concerned with color at this point since the press function itself has nothing to do with color. It's purpose is to lay down a film of ink of a certain thickness.

thx, gordon p

Gordon,

Actually the press, even if everything works properly, does not lay down the same ink film thickness for all situations at a specific SID. It actually lays down different "thicknesses" for different situations. One can even say that it is better if the plate does not have the same ink film thickness everywhere.

The important thing is not that the ink film is the same value but that the press is repeatable. That it lays down the same ink film for each specific situations but those ink films do not have to be the same. When there is consistency, not necessarily constancy, the device can be colour managed. If there is no consistency, it can be colour managed.

This is splitting hairs but it also important to understand. It explains why an Anicolor or Karat or Genius press has better overprint performance. It can only get that improved performance if the plate is inked with different ink film thicknesses. Gordon, contact me offline if you want an explanation.

About 7 years ago, when I tested my invention at Drent Goebel, I was able to get the data for the "density / relative ink film" plot in about 10 minutes. Because the press had positive ink feed due to my invention, tests on press for obtaining this curve was possible. If one wanted to, one could have run a test with weaker or stronger inks and plot their curves. These kind of curves could be then used to go to a different density by presetting the feed rate. This was successfully done during those tests.

These kinds of tests dealt with relative ink amounts in the printed film related to SID. I have never been that concerned with an actual ink film value but with such a system, it could be easily determined on press since the ink feed would not be affected by press speed, water, temperature, roller settings etc.

Also there needs to be some clarification of what "ink film" means. When one is printing, one is printing an emusified film which contains ink and water. To me the amount of water is not so important but the amount of ink is, because in the end, the water evaporates from the print and what is left is the pigment of the ink. So one could be printing different ink films (ink and water) but still be printing the same amount of pigment per area for a specific condition.

Maybe instead of talking about the ink film, one could talk about how many grams per sq. meter of ink one is printing. That is more important.

 

[gordo]

Erik. With all due respect, you are in the weeds.

To reiterate, I would like to hear the opinions of people like Achtung | Spitfire on how they measure ink film thickness - or whether it's even a concern to them.

thanks, gordon p

 

[Deleted member 16349]

Erik. With all due respect, you are in the weeds.

To reiterate, I would like to hear the opinions of people like Achtung | Spitfire on how they measure ink film thickness - or whether it's even a concern to them.

thanks, gordon p

I have been hacking away at the weeds for years. I guess I am still surrounded by them.

I would like to hear what Spitfire says also. Hope he replies.

 

[Bloodsaler]

In G7 how to book,it refers about how to monitor the color or density from CIElab,In my experience,I often monitor the Magenta ink through b*,Yellow ink through L* and b*,and the cyan ink got a big range of tolerance in my country,so I rarely notice it.And of course,the black is the easist to monitor~

 

[gordo]

In G7 how to book,it refers about how to monitor the color or density from CIElab,

Actually that's not quite correct. The G7 how to book says that you should hit the CIE Lab values and then, if you prefer, measure the densities at that point and then use those values as your target in production. (E.7.3 and E.11.2)

But it does give approximate SID values as guidance as to when the CIE Lab values should be achieved.:

E.7.2 Printing to Nominal Solid Ink Values:
C - 1.40
M - 1.40
Y - 1.0
K - 1.7

(measured Status T dry)

As I said before, solid ink density is what the press operator uses as an indirect measure of ink film thickness (not color) and, AFAIK, ink film thickness is not mentioned anywhere in the G7 how to book. So, as far as G7 is concerned, it appears that your ink film thickness can be totally unusable on press but if it hits the CIE Lab values then you are within specification. Seems odd to me.

best, gordon p

 

[pacificiam]

conclusion

conclusion

Im very thankful to all of u to share ur knowledge with me.
After reading ur opinions I found dat there is no ISO Ink density, But there are standerd LAB.

So can u plzz tell me wat are the standerd LAB valu for CMYK?