Industry standard Delta E?

[Gregg]

For offset printing, is there an industry standard Delta E to determine if the amount of color shift is acceptable?

Some scenarios (from children's book publisher perspective)

Scenario 1 - Frontlist title

• 1st printing of a 4C title
• Received & approved Fuji JetPress proofs on bulk stock

In scenario 1, we'd be looking to hold the printer accountable to be within a certain Delta E of the approved proof for the finished books

Scenario 2 - Backlist title (i.e. Reprint)

• Printer is sent hardcopy of previous printing for color match

In scenario 2, we'd be looking to hold the printer accountable to be within a certain Delta E of the previous printing for the new print run.

In scenario 2, is it realistic to ask the printer to be within X Delta E of a previously printed copy? How would the printer measure the previously printed copy, since there would not be color bars? Would they measure a specific area of a page and try to measure the exact same area on the new printing?

 

[gordo]

For offset printing, is there an industry standard Delta E to determine if the amount of color shift is acceptable?

I don't believe there is.

Some scenarios (from children's book publisher perspective)

Scenario 1 - Frontlist title

• 1st printing of a 4C title
• Received & approved Fuji JetPress proofs on bulk stock

In scenario 1, we'd be looking to hold the printer accountable to be within a certain Delta E of the approved proof for the finished books

I think that is not a good idea.
Ink jet is a different mechanical and colorant way of rendering color compared to an offset press.
When you use an inkjet's output as a proof you are looking for a visual appearance alignment - not a spectral "match".
Delta E is a good way to quantify variation within a run - but may not be valid as a target between different print methods.

Scenario 2 - Backlist title (i.e. Reprint)

• Printer is sent hardcopy of previous printing for color match

Problematic. If it's a different print shop there won't be any data to guide their press work. If it's the same print shop then they, or you, should have a full un cut press sheet as a guide. The pressroom might/should also have the press settings from the previous press run on record.

In scenario 2, we'd be looking to hold the printer accountable to be within a certain Delta E of the previous printing for the new print run.

In scenario 2, is it realistic to ask the printer to be within X Delta E of a previously printed copy?

I think not.

How would the printer measure the previously printed copy, since there would not be color bars?

That's why they, or you, kept a full press sheet on file to refer to.

Would they measure a specific area of a page and try to measure the exact same area on the new printing?

No. They would roll their eyes and do their best to visually align their presswork to the previous printed sample.

It might be an interesting exercise for you to go to the Gracol website ( Home - Idealliance ) and request an example proof and press sheet where the colors are aligned and then measure the Delta Es yourself.

Let the flaming begin LOL

 

[SteveSuffRIT]

My comments are in red color.
For offset printing, is there an industry standard Delta E to determine if the amount of color shift is acceptable?
Industry "norm" is a dE <=2.0, but depends on market segment.
Tolerance limits should be mutually agreed upon by both buyer and printer, not just dictated by buyer.
Some scenarios (from children's book publisher perspective)
Tolerance is not as critical as packaging printing, so now wider tolerance limit, maybe dE <= 2.5?

Scenario 1 - Frontlist title

• 1st printing of a 4C title
• Received & approved Fuji JetPress proofs on bulk stock
  Not sure what you mean by "bulk stock"? Most inkjet proofs are not on actual production stock.

In scenario 1, we'd be looking to hold the printer accountable to be within a certain Delta E of the approved proof for the finished books
This works if printer supplies their calibrated/profiled proof, but not someone else's proof without any colorbars.

Scenario 2 - Backlist title (i.e. Reprint)

• Printer is sent hardcopy of previous printing for color match

In scenario 2, we'd be looking to hold the printer accountable to be within a certain Delta E of the previous printing for the new print run.
This is more difficult to do so tolerance should be wider, maybe dE <=3.0

In scenario 2, is it realistic to ask the printer to be within X Delta E of a previously printed copy?
Not really fair becasue previous printer may not be printing to some standard, ISO, Fogra, Gracol, etc. Too many unknowns if matching to finished book size, without colorbars.

How would the printer measure the previously printed copy, since there would not be color bars? Would they measure a specific area of a page and try to measure the exact same area on the new printing?
Yes but area must be large enough for aperture and be uniform.
Can previous printer supply a OK press sheet with colorbars?
Best to get a close visual match by eye, regardless of dE.
Can you be at press to give a customer OK?
Why are you changing to a different printer, price, quality, what?

 

[Gregg]

Thank you, Gordo and Steve.

Herewith some additional info.

I am using "bulk stock" to mean the same stock the book will be printed on. The printers we use in Asia have the capability of running our 2 standard stocks (157gsm coated and 140gsm uncoated) on their digital proofers. A couple of our printers use Fuji Jet Press, one uses HP Indigo, and one uses an Epson model which appears to only be available in China (Sure Color SC - P9080).

Going on press would not be an option.

Not sure if the previous printer would hold colorbar proofs. We plan to ask.

We switch printers often due to schedule demands and the printers capacity, as well as price.

 

[gordo]

A small point of clarification: Steve wrote: "Industry "norm" is a dE <=2.0, but depends on market segment." An industry norm is not an industry "specification." It simply refers to the accepted thinking that a dE <=2.0 is where most people are thought to agree that two colors "match".

But it ain't necessarily so. ( thanks to Ira Gershwin )

Proofs should have color bars included and uncut press sheets should be available to refer to otherwise you don't have a basis to demand a specific dE target or tolerance.