What`s the ink density reference of commercial web printing?

[Bloodsaler]

Now I`m setting the in house density standard of our commercial web printing,but meet a problem.

Density of C1.30,M1.45,Y0.9,K1.85can within the tolrance of SWOP lab defination,but I think it`s too high for a commercial web printing,and if our printer printed according to this standard the gradation of the picture will miss,and the dot gain may become huge.
As I think C1.20,M1.20,Y0.85,K1.75 will be a good reference value of web standard,but our ink in this density can`t match the target value ,
So I want to know what`s a proper ink density reference of commercial web printing,so I can tell my ink supplier to improve our ink~

 

[gordo]

Now I`m setting the in house density standard of our commercial web printing,but meet a problem.

Density of C1.30,M1.45,Y0.9,K1.85can within the tolrance of SWOP lab defination,but I think it`s too high for a commercial web printing,and if our printer printed according to this standard the gradation of the picture will miss,and the dot gain may become huge.
As I think C1.20,M1.20,Y0.85,K1.75 will be a good reference value of web standard,but our ink in this density can`t match the target value ,
So I want to know what`s a proper ink density reference of commercial web printing,so I can tell my ink supplier to improve our ink~

The historic reference SWOP #3 solid ink density targets are:
K: 1.60
C: 1.30
M: 1.40
Y: 1.00

These SID values are an indirect measure of ink film thickness. They also help define the potential gamut.

Dot gain, TVI, gradation is a separate, different issue.

You use a tone reproduction curve applied to the plate to achieve the tone reproduction you desire. You do not manipulate solid ink density to achieve tone reproduction.

best, gordo

 

[Bloodsaler]

Yes,the solid density &TVI is seperate.
But I`ve test several print samples of my web press,our operator seems used to control the solid C1.20,M1.20,Y0.85,K1.75But under this density,only C can perfect within the tolerance of SWOP lab value.
I`m doubt wether I could require my ink supplier improve their product and make the C1.20,M1.20,Y0.85,K1.75 with in the tolerance of the lab value?

 

[Chuck Koehler]

Hello Bloodsaler,

There were never any official densities in reference to SWOP, but the ones that Gordon has listed are the most commonly accepted values. Since ISO in 2004 Industry Standards have used L*a*b* for the Target Values of Ink Colors because of the fact that density values can vary drastically according to a multitude of contributing factors.

Bottom line is that you must determine an Ink Film Thickness that you can actually print with enough tolerance to increase or decrease the ink film to adjust for color from time to time. You have two options:

1. Ask your Ink Manufacturer to help formulate your ink sets so that you can achieve the target values (in L*a*b*) while retaining some latitude to increase or decrease.

2. Reduce the amount of Ink that you are printing and possibly fall outside the tolerance range of the Standard that you are trying to achieve.

Regards,

Chuck Koehler
Print Color Specialist
Heidelberg USA

 

[gordo]

RE:

Hello Bloodsaler,

There were never any official densities in reference to SWOP, but the ones that Gordon has listed are the most commonly accepted values.

For the record (because this is an interesting bit of history)

Chuck is correct. SWOP, which is an input (i.e. primarily proofing) not printing specification did not publish solid ink density targets. Instead, they published and sold "Hi-Lo" density reference process color patches printed on a card. The printer was supposed to set their SIDs at the mid-point between the high and low density patches which represented the tolerance for each color's density.

This was done to avoid problems caused by differences in densitometers and their readings. So it didn't matter what SID that your densitometer said you were printing at as long as it was at the midpoint of what it was for the Hi-Lo patches.

The SIDs that I posted were the SIDs that are commonly published when SWOP densities are referenced and are the measured midpoints from the Hi-Lo reference (using Status T densitometry). Your SID numbers may differ as per your instrument's capabilities.

It would certainly eliminate a lot of confusion if the standards groups would publish and make available samples like that again.

best, gordo

 

[Bloodsaler]

Thanks both of your replies.Now I help my ink supplier improve our ink,so I have to set up a reference standard for her.But china`s ink maybe different from USA,not strictly according to standard for the price facor.
My supplier has posted their tested value in lab to me,it within the tolerance great,but when I use it,it hard to with in the tolerance even in a very high solid.
So I have to work with my supplier improve the ink both balance density and lab,I prefer achieve a good lab value in low density.
And are there anything else I have to let my supplier check their product?(I check the density and lab during printing and respond it to my supplier)

 

[gordo]

[SNIP]
So I have to work with my supplier improve the ink both balance density and lab,I prefer achieve a good lab value in low density.
And are there anything else I have to let my supplier check their product?(I check the density and lab during printing and respond it to my supplier)

Why do you prefer low density?

Also, what you are asking is a complex question.

The ink has to achieve a certain density otherwise you won't achieve the gamut potential and may not achieve the specifications for the standard that you are targeting or that your customers expect. Also, if your densities are too low you may have a problem with over-emulsification. I.e. the fount solution may break down the inks.
You also need to look at overprint ink trapping, ink transfer, drying time, etc., etc.

Selecting an ink is more than just density and Lab.

best, gordo

 

[Bloodsaler]

I printed my job on LWC paper,not coated or uncoated one.
As the low density I mentioned,this value is our operator usually achieved,compare with the proof,not a big problem only a gray not stay in netural.
I try very hard to change my curve of the plate,but even cyan got the smallest dot gain,the GB not improved,it`s blueish.So I decided to improve my ink,the problem may caused by magenta ink~I think~For the b* of the M ink usually around -7,too low to the standard~
I have to tell a reference density so my supplier can improve their ink according to data~

 

[Greg Imhoff]

Right first what type of Web press are you running and on what type of stocks?

Next I agree with Chuck on a need for LAB targets and with Gordo on the need for "Hi Lo" Density references. Once found request the ink supplier to provide with each shipment batches to meet speced values (-/+ ~ DE 2.00)...

Status T (Web) suggestions to hunt for possible values - may be...

1. Uncoated: C-1.10, M 1.25, Y .82, K 1.60 (+/-.10D)
2. Coated: C-1.18, M1.35, Y .90, K 1.72 (+/-.05D)

The above are suggested starting points only as it is impossible to accurately forecast needs without knowing your press and paper grades. Knowing your Ink Coverage requirements too also would help.
Plates: With the mention GRACoL (gray balance) presume you run CTP if so - check all CMYK plates to assure each is made "Linear." If not you may be "chasing the proverbial tail." Ask both your plate and ink suppliers to be on hand for any calibration and test runs.

Good luck,

Greg Imhoff
(708) 557 - 2021
[email protected]
Essex Products Group | Integrated Color Control Systems

Now I`m setting the in house density standard of our commercial web printing,but meet a problem.

Density of C1.30,M1.45,Y0.9,K1.85can within the tolrance of SWOP lab defination,but I think it`s too high for a commercial web printing,and if our printer printed according to this standard the gradation of the picture will miss,and the dot gain may become huge.
As I think C1.20,M1.20,Y0.85,K1.75 will be a good reference value of web standard,but our ink in this density can`t match the target value ,
So I want to know what`s a proper ink density reference of commercial web printing,so I can tell my ink supplier to improve our ink~

 

[BeauchampT]

Moral of the story??? Industry reference values are just that - reference.

It would be ideal if everyone could just run to the same densities, but you can't quite get it there yet. If I ran a yellow density at 1.00, I would never match my proof with the current ink we are using (we run between 1.1 to 1.15, and still have some issues). We are working on it with our supplier.

As a side point, we have had some bad experiences with our ink supplier offering to reformulate our ink to assist with better colour management. Colour gamut and DG improved beautifully; runnability of the ink on the other hand went right out the window. Best for the printer to give feedback and for the company to make small moves, not drastic, sweeping changes (we are still recovering control 3 months later).

 

[Greg Imhoff]

Bloodosaler You may be seeking to solve Gray Balance incorrectly from one single variable Densities yet may be ignoring the need for your Ink supplier to provide CMYK batch info or LAB values. Why?

It may also help you to know the optical color (Bluish or Yellowish) cast of paper or, LAB values of your paper stocks. Then adjust CTP curves sets to hit your Gray Balance NPDC, and you then have your house Densities set.

Good luck,

Greg Imhoff
(708) 557 - 2021
[email protected]
Essex Products Group | Integrated Color Control Systems

Now I`m setting the in house density standard of our commercial web printing,but meet a problem.

Density of C1.30,M1.45,Y0.9,K1.85can within the tolrance of SWOP lab defination,but I think it`s too high for a commercial web printing,and if our printer printed according to this standard the gradation of the picture will miss,and the dot gain may become huge.
As I think C1.20,M1.20,Y0.85,K1.75 will be a good reference value of web standard,but our ink in this density can`t match the target value ,
So I want to know what`s a proper ink density reference of commercial web printing,so I can tell my ink supplier to improve our ink~

 

[rich apollo]

Bloodsaler,

I think you'll have greater success if you find the colors you want your solids to be and then run to the densities that get you there. This also will give your ink manufacturer clear targets to hit.

FOGRA45L (PSO_LWC_Improved) and FOGRA46L (PSO_LWC_Standard) are datasets built from, and for, LWC papers. The solids and overprints are as follows:

LWC_Standard
paper: 90, 0, 1
C: 56, -37, -42
M: 47, 71, -4
Y: 84, -1, 88
K: 20, 1, 2
Red: 47, 65, 44
Green: 50, -56, 28
Blue: 28, 15, -42

LWC_Improved
paper: 92, 0, -2
C: 57, -37, -43
M: 48, 73, -6
Y: 86, -2, 89
K: 20, 1, 2
Red: 48, 66, 44
Green: 50, -59, 26
Blue: 28, 17, -46

Get your pressmen to run to within 5 ∆E(ab) of these values at whatever density is required. Then you can begin to decide what needs to be done.

A couple of things bother me about these data sets.
1) The magenta and the red patches have the same L* value. I'm not sure that's possible.
2) Even though the paper white of the "Improved" set is brighter, the L* values for K, Green, and Blue are the same between the two sets. As the Green and Blue exhibit hue shifts between the two sets, I would also expect to see a change in lightness between the two sets.
3) The K values are identical between the two sets even though the paper white is a different brightness and hue. I would expect to see some movement in the black solid.

 

[Bloodsaler]

I decide to use CGS ink save function to make my web sample more better~and change the EFI to CGS proof system,
Hope it can make the gray balance better~

 

[gordo]

I think you'll have greater success if you find the colors you want your solids to be and then run to the densities that get you there. This also will give your ink manufacturer clear targets to hit.
[SNIP]
Get your pressmen to run to within 5 ∆E(ab) of these values at whatever density is required. Then you can begin to decide what needs to be done.

I've never understood the thinking behind that method. In part because the primary function of a press is to lay down a film of ink - not make color. So, IMHO, I think one should lay down a proper film of ink (even, no voids, sharp demarcation between ink an non ink edges, etc.) and achieve the appropriate +/- densities. At that point the hues of your primaries and secondaries should be within the tolerances of the hues of the target you are trying to achieve. If not, and you can't achieve the hues within your SID tolerances then work with your ink vendor to select an ink series that will get you there. Using CIEL*a*b* values to determine press SIDs, IMHO, makes no sense.

best, gordo

 

[BeauchampT]

Theoretically, what you say makes perfect sense Gordo. I would love to do that.

Realistically, you have to get the job out. Sometimes you will wait months (or even years) to get all your consumables to exactly where you want them - especially if you are a multi-shop company trying to get universal suppliers. Its usually easier (in the interim) to use that method.

 

[gordo]

Theoretically, what you say makes perfect sense Gordo. I would love to do that.

Realistically, you have to get the job out. Sometimes you will wait months (or even years) to get all your consumables to exactly where you want them - especially if you are a multi-shop company trying to get universal suppliers. Its usually easier (in the interim) to use that method.

I don't understand what you mean.

best gordo

 

[BeauchampT]

Sorry. Bit tired when I wrote that. Let me rephrase.

It would be ideal to run the proper ink film and then evaluate your ink quality. Gives you a standard running condition.

Realistically though, it is far easier to run your densities a little higher to match your target Lab values. Not as good for the press, not as reliable, etc. But at least you can reach your colour gamut while you wait for the ink company/your management to make the adjustments needed.

Hopefully clearer. Really, its just an expression of cynicism

 

[gordo]

Sorry. Bit tired when I wrote that. Let me rephrase.

It would be ideal to run the proper ink film and then evaluate your ink quality. Gives you a standard running condition.

Realistically though, it is far easier to run your densities a little higher to match your target Lab values. Not as good for the press, not as reliable, etc. But at least you can reach your colour gamut while you wait for the ink company/your management to make the adjustments needed.

Hopefully clearer. Really, its just an expression of cynicism

Cynicism in the print trade? Impossible! ;-)

You're assuming that increasing the SIDs will get you to your target Lab values - which may not be the case depending on the ink hue set you're working with. I.e. the particular hue of magenta, cyan, and yellow (and somewhat black) that you're using.

best, gordo

 

[Greg Imhoff]

Appiled Densitometry

Appiled Densitometry

Bloodsaler all your Density guesses are just that.

To know - print a Digital Print Control Wedge into your normal workflows, then fingerprint your press by individual Density values with a UGRA Plate Wedge exposed on each plate.

1. Then you will see plate exposures, latitude, resolution and print curve results.
2. Next establish your Contrast values - which is to say optimum condition ink film thickness relation between Ink Densities and Dot Gain (TVI) values.
   
3. There is no other way good luck and see attached guide as this is not difficult and is rewarding.

Greg Imhoff

Right first what type of Web press are you running and on what type of stocks?

Next I agree with Chuck on a need for LAB targets and with Gordo on the need for "Hi Lo" Density references. Once found request the ink supplier to provide with each shipment batches to meet speced values (-/+ ~ DE 2.00)...

Status T (Web) suggestions to hunt for possible values - may be...

1. Uncoated: C-1.10, M 1.25, Y .82, K 1.60 (+/-.10D)
2. Coated: C-1.18, M1.35, Y .90, K 1.72 (+/-.05D)

The above are suggested starting points only as it is impossible to accurately forecast needs without knowing your press and paper grades. Knowing your Ink Coverage requirements too also would help.
Plates: With the mention GRACoL (gray balance) presume you run CTP if so - check all CMYK plates to assure each is made "Linear." If not you may be "chasing the proverbial tail." Ask both your plate and ink suppliers to be on hand for any calibration and test runs.

Good luck,

Greg Imhoff
(708) 557 - 2021
[email protected]
Essex Products Group | Integrated Color Control Systems

 

[rich apollo]

IMHO, I think one should lay down a proper film of ink (even, no voids, sharp demarcation between ink an non ink edges, etc.) and achieve the appropriate +/- densities. At that point the hues of your primaries and secondaries should be within the tolerances of the hues of the target you are trying to achieve. If not, and you can't achieve the hues within your SID tolerances then work with your ink vendor to select an ink series that will get you there. Using CIEL*a*b* values to determine press SIDs, IMHO, makes no sense.

best, gordo

Density is an indirect measure of ink film thickness that comes with a number of assumptions. Looking for a particular color is much more specific.

Second problem comes when you say, "…achieve the appropriate +/- densities. At that point the hues of your primaries and secondaries should be within the tolerances of the hues of the target you are trying to achieve.…" The key words there are should be. And what if they're not? The ink is part of a system and there are a number of factors that go into the choice of an ink: runnability, tack, drying characteristics, blanket compatibility, fountain solution compatibility, appropriateness for paper stock (say newsprint versus foil versus vinyl versus...), rub resistance, laser-safe, proximity to food, folding characteristics, coatability, temperature, et cetera, et cetera.

Changing inks is not a small undertaking.

The standard for process ink color and transparency is ISO 2846. ISO 2846 conditions are not at all similar to running on a press. And not all process ink sets are ISO 2846 compliant.

Everyone on this thread assumes that I'm talking about running the inks at higher densities. I'm talking about identifying specific color targets and finding out what you would have to do to achieve those targets. I've found that I generally have move my primary colors to hit the secondaries. Looking at specific color targets lets me find those compromises.