Describing color shift tolerance in layman's terms

[Gregg]

Not sure how that response contributes positively to this thread.

 

[chriscozi]

Not sure how that response contributes positively to this thread.

Not trying to solve the problem.
YOU pointed out that the printers you use:
1. Can't match the supplied proofs.
2. Can't match THEIR OWN proofs.
Does that NOT bear on the 'craftsmanship/smashmanship' of the printers?
And I am not the only person here bemoaning the lack of craftsmanship on the production floor and the focus on profitability over skillset.

 

[Gregg]

Gotcha. Was difficult to interpret your post, at first.

 

[danremaley]

Looking for advice on how to explain to designers that we (the customer) have to accept some variance in color which is within industry standard tolerance. What is the best way to do that.

If I was to show them this, it would do no good:
Coated Stock
C 1.45(+/-0.08)
M 1.40(+/-0.08)
Y 1.05(+/-0.08)
K 1.80(+/-0.08)

Is there a way of translating the Delta E to something the designer would better understand? For example, could you say the Magenta may move shift up to 3%. Something like that?

I realize there are so many variables, and don't want this thread to turn into super tech talk. Just wondering if anyone has a simple and easily understandable way of letting the customer know that they can expect some color shift throughout the run of their project.

Thanks in advance.

Go to System Brunner - he has examples of picture classification and process variation.
The PC Reference shows a 2-4-6% color shift to Grey. (standard deviation is +/- 2%).
That's why GCR is applied to decrease deviation of near neutral items.
Questions? Dan 412.889.7643

 

[Glenn McDowall]

∂E is super non technical. ∂ is for difference and E is for Colour.

 

[turbotom1052]

The problem with trying to assign a densitometer number variation to a 4 color printed piece is that at times a delta of up to 10 densitometer points may have a negligible affect on the bulk of the printed piece, but you may encounter images where variations of less that 5 densitometer points would greatly change the appearance of an image. Some images are just much more sensitive than others. Then there becomes the issue of variations of small amounts ( 3 densitometer points) but you may have one color 3 points high and another color 3 points low so you wind up with a hot mess thats easily noticed by even the untrained eye. Your best quality control when it comes to color is to do a regular blueprinting of both pre press and press. I would say that an annual fingerprinting would not be too frequent if you're looking to deliver top notch color control. It's also important that once youve dialed in prepress to press that you not introduce any variables into the process. Such variables to include inks, fountain solutions, blankets, plates, and even personnel, have the potential to throw things out of wack!!! Should the need arise to introduce something new into the recipe it should be done with much caution and awareness. If the change is something really significant it just may require you to do the whole fingerprint process again. I would suggest that once you get it all dialed in that you not only save samples of the finished piece, but that you also record everything in the form of density readings, dot gain, progs, and all substrates and consumables.

 

[chriscozi]

The problem . . . and even personnel, have the potential to throw things out of wack!!!

'#One' Pressman: Start density high, bring it down. Always looks 'full'.
'#Two' Pressman: Start density low, bring it up. Always looks 'light+more variation'.
We experienced this in a one month span.
Proofs never changed.
Showed the '#two' pressman same proof a month later.
Re-calibrated (fingerprinted) the press twice to convince them the machine had issues AFTER both pressman had issues meeting the proofs.
Grumbling by BOTH #one & #two stopped when units showed issues (resolved) and starting point densities were normalized.
Now stable and matches proofs again.
Sigh.

 

[SheetSqueezer]

Some images are just much more sensitive than others. .

I think FM screening helps to reduce that due to its using only one small dot size. Smaller dots have consistently less gain and therefore less color variance overall.

 

[cementary]

I think FM screening helps to reduce that due to its using only one small dot size. Smaller dots have consistently less gain and therefore less color variance overall.

Less physical gain for sure. Now optical part is always off the charts. Also one can find that those inks one using are not quite suite for FM as pigment needs to be grinded better

 

[chriscozi]

I would suggest that once you get it all dialed in that you not only save samples of the finished piece, but that you also record everything in the form of density readings, dot gain, progs, and all substrates and consumables.

This.
Have a data sheet for pressman to fill and attach to each approved sheet.

 

[davarino]

The simplest way to express this to the customer who is willing to accept that color can vary throughout a run and is often unmatchable from one process to another:

Come up with a "show and tell".

I used to use boxes (for identical hair coloring) purchased at 2 different stores to show the extremes that are possible in commercially acceptable color variance. Skin tones (and even the hair color!) would vary from store to store.

Printing is an art, a craft, something that is under the control of people who are using machines. We have tools to reduce variance, but variance will still exist.

First, see whether your customer can understand that variance occurs naturally in all processes.

If your customer cannot understand the concept of inevitable variance, you are better off without them. You will not satisfy them.

(Inability to understand variance is a mental block that is pretty much inexorable. People afflicted with this generally let this bleed into every other aspect of their lives... God help their spouses and workmates (and printers).)

 

[Gregg]

Go to System Brunner - he has examples of picture classification and process variation.
The PC Reference shows a 2-4-6% color shift to Grey. (standard deviation is +/- 2%).
That's why GCR is applied to decrease deviation of near neutral items.
Questions? Dan 412.889.7643

Thank you for those PDFs.

 

[gordo]

Being pedantic about it:

danremaley wrote: "That's why GCR is applied to decrease deviation of near neutral items."

gordo: GCR is applied wherever the three (CMY) chromatic colors print - not just near neutrals.

SheetSqueezer wrote: "I think FM screening helps to reduce that [color variation] due to its using only one small dot size. Smaller dots have consistently less gain and therefore less color variance overall."

gordo: For various reasons, most FM screening in actual production don't use just one small dot size through the tonal range.
Dot gain occurs around the perimeter of the dot. There is a greater perimeter to area ratio with small dots and therefore more initial dot gain (which is dealt with using plate curves).
The smaller the surface area of the dot the less its ability to increase its ink load. In other words, the bigger the dot the greater thickness of ink that it can hold. You can't pile a great amount of ink on a tiny dot.
So, when SIDs vary during the press run - i.e. increase/decrease in ink thickness - the ink film thickness of smaller FM dots remains more stable and therefore the color remains more stable.

 

[Gregg]

Coming back to this topic as it has come up again at work (I work at a Children's book publisher). After re-reading my OP and all of the replies I realize my wording wasn't clear. The numbers I provided were SIDs (provided to me by one of our Asian printers). What I was wondering is, by using the SIDs, was there anyway of describing how much color could shift throughout the print run.

For example C 1.45(+/-0.08) - the 0.08 refers to how much 1.45 can vary and still be considered "standard", correct?

I thought, perhaps, I could try to translate that in Photoshop but taking a cyan swatch at say 50% and then making a duplicate swatch but changing the value to 49.92 and another one at 50.08, but Photoshop only works in whole numbers.

I also realize it may not be so straightforward.

Ultimately my goal is to try and educate the Design, Production, Sales, and Editorial teams that a certain degree of color variance has to be tolerated.

 

[gordo]

[snip] What I was wondering is, by using the SIDs, was there anyway of describing how much color could shift throughout the print run

No. SIDs are an indirect measure of ink film thickness - not color. Ink film thickness is critical to the mechanics of offset lithography which is why it is important to the press operator.

[snip] Ultimately my goal is to try and educate the Design, Production, Sales, and Editorial teams that a certain degree of color variance has to be tolerated.

As I previously wrote, variations in color is very hard to communicate which is why SWOP and later Idealliance distributed printed Hi-Low ink density samples which showed the differences. Unfortunately they no longer do that.
Color variation within standards needs to be seen to be understood.
Also, measuring patches of variation in solid patches of ink (e.g. in the color bar) for a variety of reasons, may not translate into variations in the appearance of the live image area. I.e. you can be outside the SIDs standards but not see much of a difference in the live image areas.
Color variation is a show me rather than tell me situation.

 

[Gregg]

No. SIDs are an indirect measure of ink film thickness - not color. Ink film thickness is critical to the mechanics of offset lithography which is why it is important to the press operator.


As I previously wrote, variations in color is very hard to communicate which is why SWOP and later Idealliance distributed printed Hi-Low ink density samples which showed the differences. Unfortunately they no longer do that.
Color variation within standards needs to be seen to be understood.
Also, measuring patches of variation in solid patches of ink (e.g. in the color bar) for a variety of reasons, may not translate into variations in the appearance of the live image area. I.e. you can be outside the SIDs standards but not see much of a difference in the live image areas.
Color variation is a show me rather than tell me situation.

Thanks, Gordo. This all makes sense. Too bad SWOP and Idealliance no longer provide those hi-low ink density samples you mention. I completely agree with you that this is something better understood with visual references.

 

[chriscozi]

Color variation is a show me rather than tell me situation.

But, but . . . that would mean it's trade-craft - not a button-push result!
LOL
The bean counters will NOT be happy.

 

[gordo]

But, but . . . that would mean it's trade-craft - not a button-push result!
LOL
The bean counters will NOT be happy.

To be clear, if you're explaining color variation to print knowledge deficient people then you need to show them examples.

 

[chriscozi]

To be clear, if you're explaining color variation to print knowledge deficient people then you need to show them examples.

Agreed. My snark is:
If "the metric" (VISUAL-ONLY ID SAMPLES) is construed as subjective then only someone with the ability and knowledge to properly interpret "the metric" is a valued employee.
Measure measure measure.
"But why would I pay more for accuracy and quality by a specific employee if it is all about the measurement?
Can't EVERY button pusher achieve the desired result?"
Not many visual craftsmen in the front office these days by my "measure."
But I believe that used to be a road to success in litholand.

 

[A lithographer]

Looking for advice on how to explain to designers that we (the customer) have to accept some variance in color which is within industry standard tolerance. What is the best way to do that.

If I was to show them this, it would do no good:
Coated Stock
C 1.45(+/-0.08)
M 1.40(+/-0.08)
Y 1.05(+/-0.08)
K 1.80(+/-0.08)

Is there a way of translating the Delta E to something the designer would better understand? For example, could you say the Magenta may move shift up to 3%. Something like that?

I realize there are so many variables, and don't want this thread to turn into super tech talk. Just wondering if anyone has a simple and easily understandable way of letting the customer know that they can expect some color shift throughout the run of their project.

Thanks in advance.

If you are using litho and your client has a pantone reference try to steer them to have it printed as a pantone number instead of CMYK. All inks will slightly drift during production both in density and dot gain. A CMYK pantone match means 4 colours slightly drifting which will affect the hue and will throw the LAB Delta E around giving you more dramatic colour variation. A single pantone colour should only drift in density, the hue will remain more stable with the colour variation only being in saturation.