Anyone using Euclidean dot and why? Sheetfed Offset

schenkadere

Well-known member
Thanks. Odd that they claim a smoother vignette with euclidean? I can't see that. There's an optical mid bump associated with euclidean.

Seems some of that info is outdated (it is 20 years old) and maybe a sales kit for selling their screening technology.
 

gordo

Well-known member
Thanks. Odd that they claim a smoother vignette with euclidean? I can't see that. There's an optical mid bump associated with euclidean.

Seems some of that info is outdated (it is 20 years old) and maybe a sales kit for selling their screening technology.

You are completely correct.

On a side note, with AGFA Balanced Screening (I've no connection to Agfa) they take a pixel or two out of one corner of the dot when it becomes square at 50% in order to mitigate that optical bump.
But if you're using AM screening for offset, Round (non-transforming) dot is the way to print.
 

Magnus59

Well-known member
We use an elliptical dot, we di use euclidean many years ago in our Brisque days, but changed to elliptical when we switched to Prinnergy.
 

gordo

Well-known member
We use an elliptical dot, we di use euclidean many years ago in our Brisque days, but changed to elliptical when we switched to Prinnergy.

Some points about elliptical vs round:

Elliptical dot (a.k.a. Transforming Elliptical Dot, Chain Dot): Rounded corner diamond shape)
Benefits:
Optical bump is moderated by being split into two – when the dots first touch at the long width at the 40% tint and then again at the short width at 60%.
Issues: dot shape varies at different screen angles which can cause single color moiré and uneven dot gain. Dot is directional, at low lpi frequencies the “chaining” of the dots as two points touch can cause lines to appear as artifacts. Directional problems on press such as slur and doubling can cause strong tone and color shifts depending on the angle of orientation of the dots relative to the angle of the paper as it travels through the press.

Round dot: Dots are round through the tone range
Benefits:
Dot shape is the same for all screen angles and frequencies, optical bump is hidden in the shadows at the 75% tone, dot is non-directional so it is less affected by press problems. Reduces single channel moiré issues. Dot is non directional, i.e. all screen angle dots react the same to directional press issues such as slur and doubling
Issues: May not be suited for film-imaged plates because the diamond shape that results at 75% and darker tones is very sensitive to dot gain and sudden loss of shadow detail. Excellent for computer-to-plate imaging because of the greater integrity of halftone imaging as well as the ease of dot gain compensation with tone reproduction curves.
 

Magnus59

Well-known member
Some points about elliptical vs round:

Elliptical dot (a.k.a. Transforming Elliptical Dot, Chain Dot): Rounded corner diamond shape)
Benefits:
Optical bump is moderated by being split into two – when the dots first touch at the long width at the 40% tint and then again at the short width at 60%.
Issues: dot shape varies at different screen angles which can cause single color moiré and uneven dot gain. Dot is directional, at low lpi frequencies the “chaining” of the dots as two points touch can cause lines to appear as artifacts. Directional problems on press such as slur and doubling can cause strong tone and color shifts depending on the angle of orientation of the dots relative to the angle of the paper as it travels through the press.

Round dot: Dots are round through the tone range
Benefits:
Dot shape is the same for all screen angles and frequencies, optical bump is hidden in the shadows at the 75% tone, dot is non-directional so it is less affected by press problems. Reduces single channel moiré issues. Dot is non directional, i.e. all screen angle dots react the same to directional press issues such as slur and doubling
Issues: May not be suited for film-imaged plates because the diamond shape that results at 75% and darker tones is very sensitive to dot gain and sudden loss of shadow detail. Excellent for computer-to-plate imaging because of the greater integrity of halftone imaging as well as the ease of dot gain compensation with tone reproduction curves.
I might experiment with round dots, it's always dangerous to change processes in a production environment due to the risk of jobs not matching previous print. Switching from film to CTP , which we did in 1999 was a challenge due to this with curves being utilised to simulate dot gain, but we got though it and everybody got used to the sharper imaging from CTP devices.
 

gordo

Well-known member
I might experiment with round dots, it's always dangerous to change processes in a production environment due to the risk of jobs not matching previous print. Switching from film to CTP , which we did in 1999 was a challenge due to this with curves being utilised to simulate dot gain, but we got though it and everybody got used to the sharper imaging from CTP devices.
I agree.
However, if the value is there then the change is justified.
Moving from elliptical to round is much less of a change than moving from, for example, film to CtP - but you did it because, I assume, the value justified it.
 

schenkadere

Well-known member
Same here...lol

My shop was a former Heidelberg shop so I assume the euclidean thing was a left over from those days. Same as distorting plates for paper stretch compensation. I had never seen that for offset before coming here. Adds rip time.
 

kdw75

Well-known member
When our Linotronic was installed back in 1989 the installer recommended Euclidean dot and we kept using it until we bought a platesetter in 2017.
 

gordo

Well-known member
When our Linotronic was installed back in 1989 the installer recommended Euclidean dot and we kept using it until we bought a platesetter in 2017.

Did you ask the installer why?
The Euclidean Postscript spot function (round/square/inverted round) simply mimics digitally the traditional analog film-based AM halftone.
 

sveibl

Well-known member
New shop I starting working at could not match color on press. many curve attempts failed. Changed output to 175 ls round dot from 200ls Euclidean. Problem solved. not Sure if ls or round dot helped. Round dots never failed me.
 

gordo

Well-known member
New shop I starting working at could not match color on press. many curve attempts failed. Changed output to 175 ls round dot from 200ls Euclidean. Problem solved. not Sure if ls or round dot helped. Round dots never failed me.

Round dot didn't help. Switching to 175 lpi may have had an impact.
BTW Euclidean from 49% to 1% is round dot. And from 51% to 99% is inverted round dot.
 

schenkadere

Well-known member
Perhaps if you're working with film and process cameras.
Lol. I guess so. I can't imagine there's much of that left. I still can't see how that would be advantageous. Maybe to keep the shadows slightly more open. I can't imagine it would be that significant.
 

gordo

Well-known member
Lol. I guess so. I can't imagine there's much of that left. I still can't see how that would be advantageous. Maybe to keep the shadows slightly more open. I can't imagine it would be that significant.

I was thinking more in a museum of printing.

In offset, there is an interesting basic conflict in a Euclidean AM/XM halftone screen having to do with ink/water balance.

Ink Water.jpeg

The highlight and quarter tone dot range from 1-35% requires minimal water and maximum ink in order to prevent those dots from being washed away. While the three-quarter tone range from 65-99% requires the opposite - a larger volume of water in order to prevent the shadow dots from filling in and disappearing.
 

schenkadere

Well-known member
I was thinking more in a museum of printing.

In offset, there is an interesting basic conflict in a Euclidean AM/XM halftone screen having to do with ink/water balance.

View attachment 291368
The highlight and quarter tone dot range from 1-35% requires minimal water and maximum ink in order to prevent those dots from being washed away. While the three-quarter tone range from 65-99% requires the opposite - a larger volume of water in order to prevent the shadow dots from filling in and disappearing.
You find this to be significantly different than handling a round dot?
 

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