G7 AM vs. Concentric

NathanD

Active member
I ran a G7 calibration offset using Esko and object based screening to screen half the sheet at 150 AM, and the other half at 250 Concentric. The resulting TVIs threw me for a loop. The Yellow TVI for concentric is almost 10 points higher than the AM. Does this have something to do with the concentric dot structure? Or the higher line screen? Can anyone provide a technical explanation as to why grey balance would be achieved at at higher yellow dot gain with a concentric dot? Has anyone experienced similar results?

I corroborated my run vs a previous from a few years ago and the results are similar - with concentric showing higher dotgain on the yellow.
 

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The hues of the screened tones of a 250 lpi AM will be different than the screened tones of a 150 lpi AM. The difference will be exaggerated by the holes in a concentric screen. Hence the grey balance will be different. If you initially ran uncurved plates, was the yellow dot gain higher than the CMK? If so there’s a problem with either the yellow ink or that press unit.
 
The hues of the screened tones of a 250 lpi AM will be different than the screened tones of a 150 lpi AM. The difference will be exaggerated by the holes in a concentric screen. Hence the grey balance will be different. If you initially ran uncurved plates, was the yellow dot gain higher than the CMK? If so there’s a problem with either the yellow ink or that press unit.

Thanks for the reply, Gord. We didn't run uncurved plates, we ran what were our current curves at the time and adjusted from there. We knew our current curves were close to hitting G7, so we wanted to avoid making larger adjustments by doing the calibration run uncurved. After the calibration run, our adjustments to hit G7 were only a couple of points.
 
If you are going to move forward with large scale testing or are approving Concentric for production? I would strongly encourage you to seek technical guidance from industry experts like Gordo. And/or pay for training. You want your production team to have the proper training and troubleshooting skills.

We ran Concentric for years with success but the start up was very problematic. The Press-room didn't have an understanding of the ring size and spacing, so we were lost when a Pre-press technician would ask us questions. I asked for Esko and G7 training for the Press-room but was denied any help.

I wasted a lot of the company resources starting out and troubleshooting on a regular basis.
 
If you are going to move forward with large scale testing or are approving Concentric for production? I would strongly encourage you to seek technical guidance from industry experts like Gordo. And/or pay for training. You want your production team to have the proper training and troubleshooting skills.

We ran Concentric for years with success but the start up was very problematic. The Press-room didn't have an understanding of the ring size and spacing, so we were lost when a Pre-press technician would ask us questions. I asked for Esko and G7 training for the Press-room but was denied any help.

I wasted a lot of the company resources starting out and troubleshooting on a regular basis.

Appreciate the insight, CKL. The company I work for has been running concentric for years with success. I am more so just curious for my own personal knowledge from the Color side of things than from a viewpoint of concern regarding printabity.
 
We ran Concentric for years with success but the start up was very problematic. The Press-room didn't have an understanding of the ring size and spacing, so we were lost when a Pre-press technician would ask us questions.

What type of questions from prepress was the press room ill prepared to answer?
 
I asked for Esko and G7 training for the Press-room but was denied any help.

Hi CKL. I am surprised to hear that you got this response from Esko. We do offer training and assistance on both Concentric and G7. Like all training it is a payable service.
Regards, David (Product Manager at Esko)
 
Hey guys
Thanks David, I am sure it was related to the cost of the assistance and/or training. Not anything to do with Esko.

The ring and spacing questions and how it impacted the dot gain were challenging to track. We were running live work so the stocks were all different, no house stock at this shop. Lots of variables in the press room back then.

I had trouble telling prep info about the ring & spacing. I don't recall what they were specifically trying to test. I could only offer dot gain at 25/50/75 on the press sheet from a standard color bar. Since the job was a live job, I had to produce acceptable color even that meant running the inks 10 pts to 15 pts. heavier than standard. Our testing method was obviously flawed.

But the screen patches on the color bar would visually look different from job to job before they were mounted on press.

We could switch back to our standard screening and not have any issues with color matching to the proof or stability on press.
 
Our testing method was obviously flawed.

Correct. It doesn't matter what new/different screening you adopt, if you don't make the effort to do a proper implementation then you will more than likely end up constantly "fixing" press issues instead of running a production press.


But the screen patches on the color bar would visually look different from job to job before they were mounted on press.

And that didn't raise a red flag that something was wrong and needed to be dealt with in prepress rather than the pressroom?
 
Hi CKL. I am surprised to hear that you got this response from Esko. We do offer training and assistance on both Concentric and G7. Like all training it is a payable service.
Regards, David (Product Manager at Esko)

My understanding is that initial prepress setup and training is included when Concentric is purchased. Beyond that point thigh it becomes a chargeable service. Is that not correct?
 
My understanding is that initial prepress setup and training is included when Concentric is purchased. Beyond that point thigh it becomes a chargeable service. Is that not correct?

Hi Gordo. Yes Concentric is sold with standard implementation services included. The customer can purchase additional training and services as and when needed. Regards, David
 

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