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

 

[GJOHN]

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]

Concentric -> higher rulings

Concentric -> higher rulings

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.

 

[KevinC@EFI]

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

 

[DavidH]

Concentric users

Concentric users

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]

Concentric vs AM

Concentric vs AM

...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