[filmscanners] RE: Suggestions for scanning 4x5 transparencies

["Paul D. DeRocco" <pderocco@ix.netcom.com>]

Austin Franklin wrote:
>
> Also, at the end of this paragraph, they have a simple arithmetic
> error...they meant "41.67 inches (30,000 pixels /
> 720dpi)"...instead of " /
> 360"...but...they still are confusing DPI and PPI in this paragraph,
> yet they use "300ppi" (NOTE ppi) in the first sentence of this
> paragraph, so they clearly know there is a difference.  This leads me
> to believe they may be talking about something different than the
> actual input data gets resampled to 360/720 PPI, but that the dither
> algorithm works at that resolution, and has nothing to do with input
> data resampling.

The dither algorithm is the algorithm used to generate the actual pattern of
the ink dots. Since those are laid down on a 1440x2880 (or whatever) grid,
the dither algorithm obviously operates at that resolution, not 360 or 720
dpi.

It's also trivially easy to prove that the image is resampled at 360ppi or
730ppi, using a "nearest neighbor" algorithm, by constructing a test image
of alternating 1-pixel black and white lines, and printing it at various
resolutions. You can do it yourself in ten minutes.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@ix.netcom.com

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