----- Original Message -----
From: "Rob Geraghty" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, September 22, 2000 4:56 PM
Subject: Measuring resolution (was Re: Real resolution of a 4000 dpi scanner?)
> James L. Sims <[EMAIL PROTECTED]> wrote:
> > With a film target there is very likely a limiting resolution of 50 to
> > 60 line pairs/millimeter (2540 to 3048 ppi). Resolution should
> > be measured at high contrast using an etched glass plate at
> > some known spatial frequency and line width. I believe it would
> > be difficult to determine ultimate resolution using the Kodak
> > target. There are resolution targets available on glass plate
> > and etched in metal but these may be impossible to use with a film
> scanner.
>
> Does anyone have any comment about my idea of writing the
> USAF resolution target onto film using a film recorder?
> I was thinking that if it was done using a really fine grained
> film, it would be a useful way of getting a reproducible target
> for use in different scanners.
> K64 or K25 may be the only options unless I can get updated
> film settings for the recorder (which I think is a Polaroid).
>
> Rob
If you want to get "real" resolution numbers then the easiest is simply to buy
the glass test target. It actually won't be "real" even then however due to
all kinds of issues but much closer than the second option below.
If you want to get relative resolution numbers then just photograph a properly
made target. Even using my 28-80 cheap consumer zoom, I get resolution that
exceeds 4000 dpi. Works fine for relative measurements.
Cheers,
Byron
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