Paper for G7 Calibration

[TigerPress]

We have changed our house sheet from Frontier to Euro and I noticed when doing a press calibration that because the Euro is so blue (b=-4.8), that I was struggling to get a neutral gray(needed 10 point magenta cyan spread). Frontier was almost perfect with b=-0.8. Would anyone recommend using a more neutral stock for calibration even if it's not going to be the most commonly run?

 

[Asures]

Recently, I have done several G7 Master Printer - offset printing submissions and trying to find a "Compliant" paper was like pulling teeth. I have had luck with Jefferson and found that the b* was always around negative 2 -negative 3. We went through Endurance, Top Kote, and a few others. All were too Yellow with the b* going positive rather than the max tolerance of b*-4.

I would suggest that before you purchase any skids of paper, have the paper company send you a L*a*b* reading prior to delivery. If they can send you a few sheets prior to you receiving the skid, read the L*a*b* values yourself with a hand held spectrophotometer and you'll see what is acceptable or not.

Good luck!

 

[eman]

Paper for G7 Calibration

I normally use an in spec paper for the calibration, and then on the verification run tail in the house stock or out of spec paper to make sure there is still a match. The problem is the spectro's see the brightened stock as blue and we see it as white. Calculations based on this 'blue' end up pushing the yellow axis to make up for the 'blue' that we can't see. So for this reason I calibrate with a neutral paper then tail in the brightened papers to see if they will match.

Ron

 

[michaelejahn]

or, you could create a new profile for the paper...

or, you could create a new profile for the paper...

<!-- snip --!> Would anyone recommend using a more neutral stock for calibration even if it's not going to be the most commonly run?

I will assume that you understand that to get the same neutral grey on two different color paper, you need a different recipe of CMYK for each.

Perhaps you might consider contacting your favorite G7 expert who might help you decide the best approach to come up with a color managed workflow where you can create a profile & workflow for that paper.

Many of our customers use ALWAN but there are other solutions.

email us at [email protected] if you are interested in learning more.

 

[TerryWyse]

We have changed our house sheet from Frontier to Euro and I noticed when doing a press calibration that because the Euro is so blue (b=-4.8), that I was struggling to get a neutral gray(needed 10 point magenta cyan spread). Frontier was almost perfect with b=-0.8. Would anyone recommend using a more neutral stock for calibration even if it's not going to be the most commonly run?

G7 press calibration and the gray balance it produces is always relative to substrate....substrate compliance is only relevant when you start talking about specific colorimetry (GRACoL, SWOP3, SWOP5).

First off, I would always tend to recommend using whatever "house" sheet you typically use....unless your intention is try and get to GRACoL certification as opposed to just qualification status.

One strategy I use is to measure the P2P targets with both UVi and UVx filters (UV Include and UV eXclude) and then averaging the results and using this to calculate the curve adjustments......9x out of 10, the average of the UVi/UVx filtration on a too-blue paper with OBAs will be a nearly perfect a*0/b*-2. Using this for building your NPDC will generally give the right neutral balance.

A GREAT instrument to use for UVi/UVx measurements is the i1 iSis spectro since it can capture both measurements in a single pass thru the instrument.

Terry

 

[michaelejahn]

my name is (insert g7 experts name here) and I support this message

my name is (insert g7 experts name here) and I support this message

A GREAT instrument to use for UVi/UVx measurements is the i1 iSis spectro since it can capture both measurements in a single pass thru the instrument.

Yes, indeed - what Terry explained is correct - remember - G7 is a 'method' and the method is what get you to "happy"

We use the i1 iSis nearly every day, it is a great instrument.

Here is a link to a blog post;

Compose Color Blog: With Star Proof 6 spot color matching is a breeze