Best LPI ratio for Diffrent Materials
- Thread starter rafaqat
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gordo
Well-known member
Your question isn't clear.
If you're asking about image dpi to halftone lpi ratio then:
This is the deep answer: The Print Guide: Image resolution for printing - LPI vs DPI a.k.a. LPI vs PPI a.k.a. LPI vs SPI
The short answer: If the image has lots of small detail (like tree leaves) or minimal detail (like fluffy clouds) or it's being printed on absorbent newspaper you can get away with a dpi that's 1x the lpi of the screen.
If the image has lots of straight lines (like architectural) the you may want to go with a dpi that's as high as 2x the lpi
rafaqat
Well-known member
Exactly I am asking about standard output LPI s for diffrent jobs.
aqazi81
Well-known member
We used to follow 150 lpi for our print house. But most of the jobs were on boxboard and bleach.
Stephen Marsh
Well-known member
The choice of dot shape and screen ruling will be dependent on the substrate and press. Two presses running the same substrate may have to use different screens, different tone curves etc.
Stephen Marsh
Stephen Marsh
gordo
Well-known member
These are typical:
#1 coated paper - offset 175lpi
#2 paper - offset 150 lpi
Newsprint - 85-100 lpi
Flexo - 100-150 lpi
Magazines - 133-150 lpi
Of course the choice of lpi is first of all a business decision - rather than a technical decision.
For example, my local newspaper prints with a 20 micron FM halftone screen (equivalent to about 375 lpi) because of its business benefits.
gordo
Well-known member
As lpi increases (e.g. 100 lpi to 175 lpi or 175 lpi to 20 micron FM) the halftone dots through the tone range become smaller. The smaller halftone dots affect pprinting:
1- Dot gain increases - this is compensated for by the use of dot gain compensation curves applied during plate imaging.
2- The use of dot gain compensation curves to compensate for the added dot gain reduces the volume of ink needed to achieve the same visual appearance as the lower lpi screen - in some cases by as much as 30% less ink therefore production costs are reduced.
3- Smaller dots results in more ink dot area coverage for any given tone which increases the amount of light that is filtered by the ink and reduces the amount of light that is reflected unfiltered off the substrate. This has the effect of increasing the achievable gamut.
4- Smaller dots are more stable in tone and color as SIDs naturally vary during press run.
5- The higher the effective lpi the more continuous tone the image appears and the greater the detail that can be rendered.
6- The higher the lpi is when using an AM/hybrid AM screen the smaller the rosettes are and the less grainy flat tones that have rosettes will appear.
gordo
Well-known member
I guess that depends on what you mean by rough papers and boards.
Newsprint is pretty rough but can be printed using 20-25 micron FM (equivalent to about 375 lpi).
gordo
Well-known member
Ask the paper vendor for samples of printing on that paper (most paper suppliers have them) and use that as a guide.
rafaqat
Well-known member
Can I inverse your formulas to find ideal or good lpi ?
for example 2 x lpi = dpi (is to find dpi)
Lpi = dpi/2 (to find good or ideal lpi)
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