Concentric dot on sheet-fed for packaging cartons

[DavidH]

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

Harley Man,

I am employed by Esko Artwork - if you would like to PM me I will do my best to put you in touch with other Concentric customers working in a similar area.

Regards,
David

[DavidH]

...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

Gordo,

If a printer is interested in Concentric, Esko Artwork suggests they first run our standard test form. This form is simple, no obligation and compares AM against Concentric at the same ruling. We look for a measurable benefit from this test - if the printer is not convinced then they would not continue with the project.

David (of Esko Artwork)

[Toweri]

@Kevin
It seems we are talking from a little bit diffrent points of view here:

Yes, Concentric can be challenging to plate making, when the equipment are not of good quality or condition.

As David already mentioned, the very implementation of Concentric Screening at a customer site begins with a test form.
By it, it can be established whether or not the optical path of the customers recorder is of high enough quality to place sufficiently even exposure on-plate, and/or the plate and processing able to handle it, for the equipment to be able to utilise Concentric in the first place.

When the quality is confirmed (more readily on thermal recorders, LEDs close to plate; possibly more challenging to e.g. single-beam violet lasers. Their longer optical path is prone to misalignment, etc...), then the actual test measurements will be considered:
With the test form it will be established, what line width, number of rings etc. characteristics of Concentric will provide the best quality on that particular customers recorder-plate-press chain. All this is done for the customer by EAW, for free, no strings attached.

When the setup is done, Concentric should be no more challenging for plate makers to use in day-to-day production than FM screen of the same resolution.

From the printers point of view, it is even easier: More stable, more forgiving to ink feed variations during print run. And allowing to put more ink on solids, for best density, while limiting the amount of ink in screened areas, resulting in smaller dot gain and higher croma.
Of course, some these items apply to FM screen too.

The benefit of Concentric over FM is the irrefutable fact that reqular AM-type positioning of screen dots is more readily interpreted as a continuous, solid tint (as opposed to consisting of individual spots of ink) by the human visual system and the brain.

The inherent irregularity of any FM screen - by its very nature! - is far more easily detected as "graininess" by our visual cortex (that is exceedingly good at detecting shapes, by minute changes in tone.) This is the major drawback in FM, hindering its usability at lower resolutions.

@Gordo
Enabling higher rulings is actually one of the major selling points of Concentric. (I could provide you with EskoArtwork presentations stating it.)

This comes from the ink limiting properties of Concentric Screen. When the same ruling is used, the screen dots of regular AM screen are carrying much thicker layer of ink. The concentric rings of Concentric (pun intended...) limit the amount of ink per screen dot, resulting in less dot gain due to ink spreading on/in paper. Simultaneously, some of the said spread actually takes place within the dot - in-between the rings. Because of this, there is less resultant dot gain and less coalescing of dots in mid-tones. Consequently, higher rulings can be used.

PS. Just to let everyone know: I work for a local distributor of EAW. English is not my native language, I may have used odd terminology or expressions here...

[rich apollo]

I was wondering about the test form. Having the two screenings on the same set of plates might not work at all. I've run a similar test with conventional and FM screens. The ink and water demands of the different screens were too dissimilar to draw any useful comparisons.

[gordo]

Gordo,

If a printer is interested in Concentric, Esko Artwork suggests they first run our standard test form. This form is simple, no obligation and compares AM against Concentric at the same ruling. We look for a measurable benefit from this test - if the printer is not convinced then they would not continue with the project.

David (of Esko Artwork)

Printers are very good at production - very few are good "test pilots" i.e. doing analytical testing of new technologies.
I don't know how your test form is explained to customers during the sales cycle, however, I do know something about comparing screening. Your test form consists of a single color run using cyan or magenta.
If the customer examines the Concentric and AM screening at the same tone value at the same lpi they will see this:

Since the color we see and measure is the result of light being filtered by the ink - I do not see any way that gamut can be increased by using a dot that increases the amount of light that that is not filtered by the ink.
That fact is confirmed if one measures the color, as was done here:

The green dots are 175 lpi AM the red dots 175 lpi Concentric. The higher the dot the greater the chroma.
As you can see the difference in chroma is negligible with the Concentric having very slightly less. So I don't see any benefit as regards chroma.

The above was taken from Esko printed marketing materials.

Because the screens have the same lpi they have the same detail rendering capability - so I don't see any benefit there.

So, I cannot see or measure a benefit. If you could explain what the benefit is that the printer would see comparing the different screens at the same lpi, then I would sure like to understand it. So far no Concentric user, including Esko, has been able to provide data to support any benefit.

If you could send me an example of one of the test press sheets that you have customers print so that I could measure that - I would really appreciate it. I'll happily pay for shipping.

best, gordon p

[gordo]

[SNIP]
Yes, Concentric can be challenging to plate making, when the equipment are not of good quality or condition.
[SNIP]
By it, it can be established whether or not the optical path of the customers recorder is of high enough quality to place sufficiently even exposure on-plate, and/or the plate and processing able to handle it, for the equipment to be able to utilise Concentric in the first place.

When the quality is confirmed (more readily on thermal recorders, LEDs close to plate; possibly more challenging to e.g. single-beam violet lasers. Their longer optical path is prone to misalignment, etc...), then the actual test measurements will be considered:
With the test form it will be established, what line width, number of rings etc. characteristics of Concentric will provide the best quality on that particular customers recorder-plate-press chain.[SNIP]
When the setup is done, Concentric should be no more challenging for plate makers to use in day-to-day production than FM screen of the same resolution.

I agree with that.

From the printers point of view, it is even easier: More stable, more forgiving to ink feed variations during print run. And allowing to put more ink on solids, for best density, while limiting the amount of ink in screened areas, resulting in smaller dot gain and higher croma.
Of course, some these items apply to FM screen too.

From your last sentence you seem to be comparing Concentric with AM. If you are comparing them at the same lpi then - from what I can determine there will be no increase in gamut/chroma (see my response to DavidH). I can't speak to the issue of what happens when solid ink varies. If you have data or examples to support your claim of greater stability - I would sure like to see it. I will pay for shipping if it's a physical sample.

[SNIP}
The inherent irregularity of any FM screen - by its very nature! - is far more easily detected as "graininess" by our visual cortex (that is exceedingly good at detecting shapes, by minute changes in tone.) This is the major drawback in FM, hindering its usability at lower resolutions.[/SNIP]

That is true of old-style first order FM screens. It may also be true of some modern second order FM implementations it the imaging system was not capable (but then the imaging system would not be qualified for Concentric either. Graininess is not true of the majority of modern FM implementations. All I can say it that over 75% of submissions for the international Benny print awards (the most prestigious print awards) are done with FM screening. FM screening is also representative of the majority of winners.[/quote]

@Gordo
Enabling higher rulings is actually one of the major selling points of Concentric. (I could provide you with EskoArtwork presentations stating it.)

Please send me this because none of the Esko material I have states that. pritchardgordon @ gmail (dot) com

This comes from the ink limiting properties of Concentric Screen. When the same ruling is used, the screen dots of regular AM screen are carrying much thicker layer of ink. The concentric rings of Concentric (pun intended...) limit the amount of ink per screen dot, resulting in less dot gain due to ink spreading on/in paper. Simultaneously, some of the said spread actually takes place within the dot - in-between the rings. Because of this, there is less resultant dot gain and less coalescing of dots in mid-tones. Consequently, higher rulings can be used.

Dot gain does not limit line screen rulings since it, whether - AM or Concentric - can be dealt with by the use of a plate curve.

You say that "the screen dots of regular AM screen are carrying much thicker layer of ink."
Well, below is a heightmap rendering of Concentric (on left) vs AM (on right) both at 175 lpi. (using the image in my response to DavidH as the basis) Here, relative density - i.e. solid ink film thickness is mapped to height.

If the AM screen in this case has an ink an ink film thickness of 1.5 microns then this indicates that the ink film thickness of Concentric has an average thickness of 1.36 microns. I think a difference of 0.14 microns - about 8% - hardly represents a much thicker layer of ink for the AM screen. If you have press sheets of Concentric vs AM at the same lpi but at different SIDs, I would love to see them and measure the relative ink film thicknesses as SIDs change.

best gordon p