Making color standard book with Light - Standard - Dark in offset printing

[thaiha]

Dear all,
I'm new member. I need advice from all of you the way to making standard book with Light - Standard - Dark.
The current method I'm doing is using tolerance of density reference with GRACoL page 21, Section 6.2 - Calibrating, Printing and Proofing
Cyan 1.45+/-0.1
Magenta 1.45+/-0.1
Yellow 1.0+/-0.07
Black 1.7+0.2-0.05

I will making the standark tone first, then record density of all inks.
Second reduce (-0.1) density of all ink compare with standard --> light tone
Finally increase (+0.1) density of all ink compare with standard --> dark tone

So, I need get advice from all of you, If you have any method to do better.
Thanks all
Thaiha

 

[gordo]

Dear all,
I'm new member. I need advice from all of you the way to making standard book with Light - Standard - Dark.
The current method I'm doing is using tolerance of density reference with GRACoL page 21, Section 6.2 - Calibrating, Printing and Proofing
Cyan 1.45+/-0.1
Magenta 1.45+/-0.1
Yellow 1.0+/-0.07
Black 1.7+0.2-0.05

I will making the standark tone first, then record density of all inks.
Second reduce (-0.1) density of all ink compare with standard --> light tone
Finally increase (+0.1) density of all ink compare with standard --> dark tone

So, I need get advice from all of you, If you have any method to do better.
Thanks all
Thaiha

What is the point of what you're doing?

 

[thaiha]

Finding the best way to making color standard with light - Standard - Drak tone for production

 

[Tim-Ellis]

Hello Thaiha,

We used to use colour standards a lot. We try to avoid it now.


Let us see if I have understood you correctly. You have this four colour job. You want to print a colour standard for your own reference.

One colour standard will be the lightest acceptable print.

One colour standard will be the darkest acceptable print.


I have some questions for you:

Will these colour standard sheets be used just in your print shop or will they be sent to other print shops or clients?

Will people just be using their eyes to look at these colour standards to decide if the print colour is acceptable?

You have a Densitometer. Do you also have a Spectrophotometer?

What kind of press are you using?

 

[thaiha]

Dear Tim-Ellis,
Pls see my reply below:

Will these colour standard sheets be used just in your print shop or will they be sent to other print shops or clients? --> Thaiha: These colour standard sheets will be use for our print shop and clients also.

Will people just be using their eyes to look at these colour standards to decide if the print colour is acceptable? --> Thaiha: People use their eyes then use Spectrophotometer to measure density and Delta E for reference.

You have a Densitometer. Do you also have a Spectrophotometer? -->Thaiha: We have Desitometer and Spectrophotometer also.

What kind of press are you using? --> Thaiha: We have 3 Komori (6 color units + 1 coating unit), 3 Komori ( only 2 color unit), 1 KBA (7 color + 2 coating unit) and 1 Roland (6 color unit + 1 coating unit)

 

[thaiha]

Yes, you are correct Tim-Ellis.
We always print not only 4 color but also to 7, some time to 9 color.
C, M, Y, K and some spot colours

 

[Cornishpastythighs]

We stay well away from doing 4 colour CMYK process lights/Darks as the process never follows what we would produce on press. For instance you will simulate on your standards all colours going up say 5 points in density where as on the press only the magenta may go up 5 points but the yellow or cyan may go down 5 points, you cannot simulate this in your lights/darks as the combinations would be endless. example. cyan up magenta up yellow down. We have not even covered the effect of dot gain and how it could affect process colour lights/darks.
We do lights/darks only for the special colours and we have around 2000 at the moment. Some are sent to the customer at their request and some are only used inhouse to make good/no good decisions.
We concentrate on reducing as much as possible the causes of variation and conduct regular process capability studies on our presses to check they are performing within our tolerance.
We have a great ink inplant and we verify their inks match using Spectro on press so we know we are starting off with the correct colour.
Not saying this is perfect but it is what we do and so far it has worked for us.
Good luck

 

[DeltaE]

Ink density variation during printing process always happens. But you can control it:
- run enough make-ready sheet then take sample sheet. Check it by visual or by spectrometer, correct it if you want. Repeat until you accept with the color. Then full speed ahead. So you have only 1 kind of color in whole pack of printed sheets. No light color, dark color which confuses you and your client.

Same as cornishpastything, you can not make the light, dark limit for combination of 4 color Cmyk.

Hope this helps you some!
rgds,
DeltaE

 

[gordo]

Hi-lo reference patches are typically used in packaging for spot and brand colors. They can also be used for solid process inks as was done by SWOP in order to eliminate the issues around inter instrument agreement. But there are too many variables to make it useful as a guide for imagery.

 

[thaiha]

Dear all,
C,M,Y,K is really complicated and impossible for making light and dark limit as DeltaE said --> so, what is the best way to make sure each of printed lot is the same ( previous lot - current lot - next lot)? cause there are so many factors impact to half-tone process. Each of factor will make colour change a bit.
What standard can accept with difference a bit ? or process colour need to be exact as a requirement?

Normally, what value of Delta E we use in offset printing industrial, I knew that for ISO 12647-2 ( version 2013) they recommend to 5. But Delta e value is 5 really different ? And ISO 12647-2 version 2013 only mention for Delta E value for process color, it do not mention for spot color.


Dear Gordo,
Can you make clear: Hi-lo reference patch ?

 

[gordo]

Dear Gordo,
Can you make clear: Hi-lo reference patch ?

OK. Instruments (densitometers, spectrophotometers) that are used to measure ink vary in their accuracy (see the chart at the end of this post as an example). So, two instruments - even calibrated ones - may give different values when measuring the same patch of color. So, giving a density or Lab value as a target for presswork can result in variation in final color as adjustments are made to align the color to the specification according to an individual instrument's readings.

A high-lo reference patch is designed to eliminate the lack of inter-instrument agreement. It is a printed sample of the ink (spot, Brand, or process) that is printed at the highest and lowest acceptable solid ink density. The printer measures those two patches and whatever value their specific instrument gives them for those two patches - that is the density tolerance that their printing should fall between. The printer figures the midpoint between those two values and sets that as their target.

This is the method used for many years by SWOP and if you were a publications printer you could buy the hi-lo reference from the SWOP organization.

The same method has been used for many years by brand owners (e.g. Proctor and Gamble, Kraft, etc.) to control their brand colors. The brand owner would supply their printers with hi-lo reference swatches which functioned like the SWOP ones above.

These reference patches are often (but not always) put into a 3 ring binder - numbered and assigned to the specific printer.

Here is a photo of Kodak's hi-lo reference:

The holes are there so that a visual check can also be made.

Here is the Post cereals brand manager checking the presswork with his hi-lo reference:

Often, the brand owner will directly supply the printer with the brand ink in order to eliminate variation caused by different ink companies mixing the ink themselves. It also makes brand color control the responsibility of the brand owner rather than the individual printer.

The high-lo reference is also used because solid ink density (not color) is the only control the press operator has - so the reference is an effective tool for the printer.

The same thinking applies to process colors.

The solid reference patches can also be used to provide Lab values if desired.


Results of one test of instrument variability expressed as deltaE:

 

[Cornishpastythighs]

Wow I love Kodak's Hi/Low for the yellow

 

[thaiha]

Dear Gordo,

Many thanks for your advice.

To follow with your advice, the all parameters (TVI, Gray balance, Trapping & Registration ...) had to correct in standard, if not, it is no meaning. Am I correct or not ?

 

[gordo]

Dear Gordo,

Many thanks for your advice.

To follow with your advice, the all parameters (TVI, Gray balance, Trapping & Registration ...) had to correct in standard, if not, it is no meaning. Am I correct or not ?

Yes. And of course there shouldn't be any issues like slurring, doubling, over or under emulsification etc.