Concentric dot on sheet-fed for packaging cartons

[Harley Man]

Does anyone use Concentric dots on a sheet-fed press for packaging cartons. And if so how do you like it compared to regular dots. Any problems?

Thanks
Harley Man

[gordo]

Does anyone use Concentric dots on a sheet-fed press for packaging cartons. And if so how do you like it compared to regular dots. Any problems?

Why are you considering that screening method?

best, gordon p

[Harley Man]

Why are you considering that screening method?

best, gordon p

We use that dot in our shop. I just wanted to get other opinions about this screening method.

Harley Man

[George John]

I found a good explanation of concentric dots at www.highdefprint.com/concentricdot/htm
hope this is heplful to all.

[gordo]

I found a good explanation of concentric dots at www.highdefprint.com/concentricdot/htm
hope this is heplful to all.

That explanation is just a reprint of Esko's marketing material.

@Harley Man

This question has come up several times in this forum. So far, it appears that no one has done a measured comparison of the presswork performance of Concentric with AM/XM at the same lpi - e.g. 175 lpi Concentric against 175 AM/XM. (or 210 or 250 lpi). There are no published ICC profiles of Concentric and AM/XM at the same lpi - e.g. 175 lpi where one could compare gamuts. From my own testing - based on one Esko published sample - shows that there appears to be no significant difference in gamut between 175 lpi AM/XM and 175 lpi Concentric.

Have you made direct comparisons yourself? If so what has been your experience?

thx, gordon p

[Harley Man]

That explanation is just a reprint of Esko's marketing material.

@Harley Man

This question has come up several times in this forum. So far, it appears that no one has done a measured comparison of the presswork performance of Concentric with AM/XM at the same lpi - e.g. 175 lpi Concentric against 175 AM/XM. (or 210 or 250 lpi). There are no published ICC profiles of Concentric and AM/XM at the same lpi - e.g. 175 lpi where one could compare gamuts. From my own testing - based on one Esko published sample - shows that there appears to be no significant difference in gamut between 175 lpi AM/XM and 175 lpi Concentric.

Have you made direct comparisons yourself? If so what has been your experience?

thx, gordon p

I saw a test sheet for a customer that has a pictorial with concentric 250 and regular dot on the same sheet and I have to say that the concentric does look sharper more detail.
But I have not run any tests.

Harley Man

[gordo]

I saw a test sheet for a customer that has a pictorial with concentric 250 and regular dot on the same sheet and I have to say that the concentric does look sharper more detail.
But I have not run any tests.

If the concentric and regular AM/XM dot are run at the same lpi (i.e. both at 175 lpi or both at 250 lpi) they will look identical.
However, if the Concentric is run at 250 and the AM/XM is run at 175 then the Concentric will have more detail. That is how it is usually demonstrated/tested.

best, gordon p

[Toweri]

Isn't one of the points of Concentric to enable the use of higher rulings. This is due to its intrinsic ink limiting characteristics.
In that sense, it is valid to compare e.g. 250 lpi Concentric with 175 lpi AM. It will indicate the benefits of Concentric in real-life configuration.

[Kevin@Kodak]

Isn't one of the points of Concentric to enable the use of higher rulings. This is due to its intrinsic ink limiting characteristics.
In that sense, it is valid to compare e.g. 250 lpi Concentric with 175 lpi AM. It will indicate the benefits of Concentric in real-life configuration.

Gordo - you probably remember this, but the testing our imaging team did internally showed that the challenges of imaging (and printing) concentric screening were the same or harder than fine FM screening, while the claimed benefits were basically the same.

From the perspective of just getting the rings onto the plate in the first place, you have the same challenge as FM: consistent/sharp rendition of fine features. Second, you have a unique problem which is worse with some imaging technologies than others: it highlights any differences in horizontal fine-line quality versus vertical fine-line quality. Not all imaging devices perform identically in both directions (Kodak SQUAREspot would be one of the few/only exceptions). I.e., vertical lines might be wider/narrower or sharper/blurrier than horizontal ones. When you get into the finest lines you'll see that as areas that disappear altogether or wear quickly on press.

Our measurement of how difficult a particular screening is -- and the capability of a particular CTP/plate/processing combination to support it -- is based on the frequency of dot-edge transitions. Even moderate concentric screens have more frequent edge transitions than 10-micron FM. This makes them MUCH more sensitive to process changes than coarser screens and FM screens, and dramatically reduces system latitude and consistency.

Our conclusion based on testing was that the benefits are claimed to be similar between FM and concentric screening, but the challenges are much harder with concentric... so why go that route instead of FM?

Kevin.

[gordo]

Isn't one of the points of Concentric to enable the use of higher rulings. This is due to its intrinsic ink limiting characteristics.
In that sense, it is valid to compare e.g. 250 lpi Concentric with 175 lpi AM. It will indicate the benefits of Concentric in real-life configuration.

No, it is not to enable higher rulings. That is not a claim made by Esko. The actual claim made by Esko is (and I quote): "The function of the Concentric Screen is to provide the benefits of stochastic without the grainy appearance." I'm assuming that they are referring to their implementation of stochastic since a "grainy appearance" is not a characteristic of all stochastic screens.

Also, designing an AM dot so that it requires a higher level of imaging integrity than an equivalent lpi conventional AM dot seems hardly conducive to enabling higher screen frequencies.

You can run AM/FM screens much higher than 175 lpi. (I believe the record is still 1670 lpi done by Metropolitan Fine Printers in Vancouver). So it is completely fair to compare 175 or 250 lpi concentric to 175 or 250 lpi conventional AM/XM. If you want to stay with an AM screen and want to use 250 lpi - then compare 250 lpi Concentric to 250 lpi conventional. If you can't see/measure a meaningful difference then IMHO go with the 250 lpi AM/XM as it will be more forgiving on your imaging system.

best gordon p