ISO Standard Ink Densities

[Gregg]

Hi.

One of our main printers in Asia sent me this stating these are the ISO Standard Ink Densities that they follow.

ISO standard

C 1.45(+/-0.08)
M 1.40(+/-0.08)
Y 1.05(+/-0.08)
K 1.80(+/-0.08)

I tried to find anything online to confirm that these are accurate, but am unsuccessful.

Do these numbers look correct?

Also wondering if this is for coated stock only, or if it covers both coated and uncoated (the 2 stocks we print on).

 

[Cornishpastythighs]

This is for coated stock I believe and they look pretty close to the numbers we used to shoot for, maybe flip the cyan/ magenta values

 

[realaqu]

Hi.

One of our main printers in Asia sent me this stating these are the ISO Standard Ink Densities that they follow.

ISO standard

C 1.45(+/-0.08)
M 1.40(+/-0.08)
Y 1.05(+/-0.08)
K 1.80(+/-0.08)

I tried to find anything online to confirm that these are accurate, but am unsuccessful.

Do these numbers look correct?

Also wondering if this is for coated stock only, or if it covers both coated and uncoated (the 2 stocks we print on).

I believe there is no such thing in iso standard, only LAB value defined for each color

 

[Gregg]

When researching, I am also finding most articles point to LAB values.

Wonder if this printer is just working to extremely old standards.

The reason for my initial question is we always have issues in which are printers aren't able to match the proofs provided by our repro houses.

"We run to standard ink densitites" is often claimed as they point fingers at each other.

 

[jimas67]

They look a little high but they look close to standard start up for coated offset.

 

[gordo]

Hi.

One of our main printers in Asia sent me this stating these are the ISO Standard Ink Densities that they follow.

ISO standard

C 1.45(+/-0.08)
M 1.40(+/-0.08)
Y 1.05(+/-0.08)
K 1.80(+/-0.08)

I tried to find anything online to confirm that these are accurate, but am unsuccessful.

Do these numbers look correct?

Also wondering if this is for coated stock only, or if it covers both coated and uncoated (the 2 stocks we print on).

The official published SIDs for sheetfed on premium coated paper the values were
Yellow 1.05
Magenta 1.50
Cyan 1.40
Black 1.70

For uncoated they were:
Yellow 0.95
Magenta 1.12
Cyan 1.00
Black 1.25

This is for a KCMY sequence, 175 lpi - i.e. GRACoL status T unpolarized. Since these values are from measuring dry patches, the press operator should be running the inks a bit higher in density so that when dryback occurs the density hits those SID values.

So, your printer is in the ballpark with their SIDs. There can be many, many reasons (I could list some if you want) why the printers aren't able to match the proofs provided by your repro houses.

BTW, the standards have abandoned SIDs in favour of Lab target values. I think that this is because the standards groups don't understand that offset presses are not engineered to print color - they are engineered to lay down a film of ink on a substrate. Don't get me started on this. ) :- P

 

[SteveSuffRIT]

Gregg, I wonder why you didn't post this on your original thread on May 3 for "How to differentiate ISO 1`2647 vs Fogra"?

For calibration, you find the lowest Delta (dE) based on Lab, checking hue angle (h').
For process control, you use its corresponding solid ink density (SID).
The +/-0.08 is a little wide. Most printers use +/-0.05.
Black ink on gloss coated paper, without any WB/AQ coating, can have >0.10+ of dry back, occurring within the first 30 minutes.

 

[SheetSqueezer]

I tried to find anything online to confirm that these are accurate, but am unsuccessful.

Do these numbers look correct?

Also wondering if this is for coated stock only, or if it covers both coated and uncoated (the 2 stocks we print on).

The numbers you listed represent coated SIDs, and depending on the ink they’re using and their equipment calibrations, are probably fine (in practice, there’s no such thing as industry wide SIDs). Although for better color consistency, the +/-.08 tolerances you listed should probably be cut in half. Good luck telling that to a printer that’s halfway around the world, though.

 

[Gregg]

Printer came back with this for uncoated (woodfree) stock

ISO standard for woodfree paper
C 1.05(+/-0.08)
M 1.05(+/-0.08)
Y 0.9(+/-0.08)
K 1.20(+/-0.08)

This is a bit off from what Gordo had shared. Since this printer is in Asia, which recognizes/follows FOGRA rather than GRACoL, I wonder if that could be the reason for the slightly different values.

 

[gordo]

Printer came back with this for uncoated (woodfree) stock

ISO standard for woodfree paper
C 1.05(+/-0.08)
M 1.05(+/-0.08)
Y 0.9(+/-0.08)
K 1.20(+/-0.08)

This is a bit off from what Gordo had shared. Since this printer is in Asia, which recognizes/follows FOGRA rather than GRACoL, I wonder if that could be the reason for the slightly different values.

I believe that Asia uses Status E polarized (like Europe) rather than Status T unpolarized instruments as in America.
Also, often printers think the target numbers refer to wet rather than dry measurements and print accordingly.
Unfortunately (from my experience anyway) the standards groups don't include actual press operators and don't always understand the process they're setting standards for - at least from my experience being on the idealliance council and attending a few of the verification print runs for GRACoL.

 

[Gregg]

Overnight, I confirmed with this specific printer that their ink sequence is KCMY.

Our main repro house has recently switched to CMKY - using 2 separate 2-color presses to produce their wet-proofs.

Am I correct in thinking the difference in ink sequencing would make it near impossible to match the Repro wet-proofs?

 

[gordo]

Overnight, I confirmed with this specific printer that their ink sequence is KCMY.

Our main repro house has recently switched to CMKY - using 2 separate 2-color presses to produce their wet-proofs.

Am I correct in thinking the difference in ink sequencing would make it near impossible to match the Repro wet-proofs?

In this case I doubt it since the chromatic colors are effectively in the same sequence. I.e. both are CM and Y at the end.

 

[SteveSuffRIT]

Comparing apples to apples?
When comparing density measurements, measurement conditions are important.
Paper included (absolute) or excluded (relative), wet or dry, backer (white, black, self), filter response, ect.
Status T uses a 47 blue filter for yellow ink, wide band (~100nm)
Status E uses a 47B blue filter for yellow ink, narrow band. Because less light passes thru the narrower band, yellow density will be much higher. Higher value is better signal/noise ratio (more sensitivity to changes in ink film thickness (IFT).

While Solid Ink Density (SID) is important, the size of the dot (dot gain) or Tone Value Increase (TVI) is more important on having an effect on the resulting "color" appearance.
Can you share dot gain values? (asked this in the May 3rd thread "How to differentiate ISO 1`2647 vs Fogra")

 

[Gregg]

Comparing apples to apples?
When comparing density measurements, measurement conditions are important.
Paper included (absolute) or excluded (relative), wet or dry, backer (white, black, self), filter response, ect.
Status T uses a 47 blue filter for yellow ink, wide band (~100nm)
Status E uses a 47B blue filter for yellow ink, narrow band. Because less light passes thru the narrower band, yellow density will be much higher. Higher value is better signal/noise ratio (more sensitivity to changes in ink film thickness (IFT).

While Solid Ink Density (SID) is important, the size of the dot (dot gain) or Tone Value Increase (TVI) is more important on having an effect on the resulting "color" appearance.
Can you share dot gain values? (asked this in the May 3rd thread "How to differentiate ISO 1`2647 vs Fogra")

Thanks, Steve. Will ask that question next.

 

[Gregg]

Got some feedback from the Repro House, which seems to me more in line with what folks here are stating.

Response from Repro:
"Frankly, we believe ISO 12647 did not really specify the ink density, but specified the Lab value for the CMYK ink. However, we agree the ink density could provides a good guideline to control or help us to achieve a closer Lab target from ISO. Besides, ISO recommends we should achieve the correct colour (Lab values) of CMYK for a specific paper first before determine the ideal ink density. Therefore, different printers may applied a different inking density (usually the difference may not be large) according to their materials (different brands of ink and paper) and equipments, so as to get closer match to the Lab values specified by ISO."


Am I correct in thinking LAB values are measured using a Spectrophotometer?

Are the color bars what is measured for LAB values?

 

[SteveSuffRIT]

Color or Quality bar contains patches or blocks of solid inks to be measured with a spectrophotometer (handheld or scanner), like an X-Rite or Techkon.
Lab values get converted into Delta E (dE) color difference for calibration (fingerprint or ICC profiling).
Corresponding SID (density) & TVI (dot gain) are then often used for production process control because they are more familiar/understood by press operators.

While SID is important and effects TVI, TVI is more important and effects the final color appearance more so! SHOW ME THE TVI!

 

[SheetSqueezer]

Printing presses use either handheld scanners, scanners at the console, or scanners in the press itself. All of them are measuring for ink density because that’s what’s used to adjust for color. The ink densities they’re adjusting to are established long before the printing process, with press calibration. Obviously there’s more than one system to try and match to but the best way that I’m aware of is to profile and calibrate presses to achieve a G-7 certification. G-7 calibration is done by measuring TVI, Delta, and Lab values. Machines that get certified can then theoretically match color very closely to each other, whether it‘s digital, offset, within the same shop or from different locations.

 

[gordo]

SteveSuffRIT wote:

"Corresponding SID (density) & TVI (dot gain) are then often used for production process control because they are more familiar/understood by press operators."

SheetSqueezer wrote:

"Printing presses use either handheld scanners, scanners at the console, or scanners in the press itself. All of them are measuring for ink density because that’s what’s used to adjust for color."

The reason press operators measure SIDs is because that, with corresponding water volume, is one of the only adjustment controls a press operator has. The importance of that is that SID values provide an indirect measure of ink film thickness. Laying down an ink film is what presses are engineered to do. Offset lithography only operates within a narrow range of ink film thickness. Too thick or too thin and the mechanical process will fail. The range of thickness is typically between 0.7 and 1.2 microns. That's a very narrow 0.5 micron range. For context, the thickness of a human hair is around 20 to 30 microns.
Changing SIDs to adjust color is only done because that's the only adjustment option the poor press operator has rather than because it's the right method. A hammer can drive a screw into a piece of wood but that doesn't make it the right tool for the job.