150lpi vs 175 lpi

[maks]

i am printing on a claycoated board for folding carton milk boxes - will i have better print control if use 150 lpi or 175 lpi. and how will the graphics compare to the differing lpi?

thanks

 

[KimR]

I would go with 150 lpi, 150 lpi is good for 300 PPI images. It is a myth to have images at 300 PPI or what people claim 300 DPI which is incorrect. Images should be double of what the lpi is. 150 lpi would be much easier to control.
In saying that we do a lot of one side poly at 175 line

 

[SteveSuffRIT]

Generally, lower lpi is more "controllable" or "stable" on press.
However, the tradeoff is visual resolution and detail.
I would output same image at 150 & 175, print test it to compare.

 

[maks]

Generally, lower lpi is more "controllable" or "stable" on press.
However, the tradeoff is visual resolution and detail.
I would output same image at 150 & 175, print test it to compare.

thanks for the reply. on a conventional am screening, is it still okay to go for 200lpi just to improve the details?

 

[KimR]

If you go to 200lpi, I would want images @400ppi.

 

[gordo]

KimR wrote:
"It is a myth to have images at 300 PPI or what people claim 300 DPI which is incorrect. Images should be double of what the lpi is."

Gordo: Image dpi/ppi can have a resolution anywhere from equal to to double the lpi. e.g. for a 150 lpi screen the range can be from 150 dpi to 300 dpi at 100% reproduction. This is easy to confirm by simply testing it.

SteveSuffRIT wrote: "Generally, lower lpi is more "controllable" or "stable" on press"

Gordo: "controllable" is not the same as "stable"
In the sense that lower lpi allows the press operator to affect SIDs to vary tones/color, yes, a lower lpi is more controllable. Of course this also means greater variations in presswork as SIDs naturally vary on press.
As variations is SIDs naturally occur on press - higher lpis produce more stable tones/color. I.e. tones/color become more stable as lpis are increased - so 200 lpi will deliver more stable presswork than 150 lpi as SIDs vary.

This is easy to prove on press.
.

 

[maks]

very confusing now. will it mean it is best to go for 200 lpi even on coated board (grayback). will the fine dots at 200m lines hold consistently? thanks for the expert answers. well appreiciated

 

[gordo]

Without knowing your specific print condition, I think that only general info can be given.

This press is running 20 micron FM on grey board for packaging:

But that doesn't mean that you are able to.
Can you run a test?

 

[KimR]

Just go with #175! 200lpi is overkill

 

[sveibl]

I would love to see test results also! I remember when going from 133 to 150 was a challenge