> LPI, however, still eludes me somewhat. You speak about LPI in graphics
> arts terms, the halftone ruling being specified in these units.
Hi Tom,
In the graphic arts term, especially when they still use halftone screen to
make halftone, the number of lines become the number of dots, so in that
*context* dpi would be the same as lpi. I think confusion arises after we get
into digital where dpi is the addressable resolution whereas lpi is (can be)
the result.
> However, I have also seen lines-per-inch as a unit for specifying the
> resolving power of a lens or film. In this context, a very fine pattern of
> alternate black and white lines is photographed at different magnifications
> using the lens or the emulsion being analyzed.
You can think of lpi or dpi simply as a unit.
> But now it rather seems to me that the term LPI is context- dependent.
Yes, and same also with dpi. For example, dpi for an imagesetter refers to
the dots which can be opaque or clear, whereas dpi for film recorder refers
to the dots which can be full color. Now they start to use ppi (pixel per
inch) to distinguish things, but the fact is the terms have not been
standardized yet, so it is important to check the context.
Dave Soemarko
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