[filmscanners] Re: The"Pepper Grain" problem

["dickbo" <dickbo@btopenworld.com>]

Your quite wrong of course. Depth of field is that area either side of an
OBJECT - in this case it would be the original transparency or negative -
within which it is considered to have produced an acceptably sharp image -
however you care to define sharpness is not an issue here.

----- Original Message -----
From: "Austin Franklin" <darkroom@ix.netcom.com>
To: <dickbo@btopenworld.com>
Sent: Wednesday, April 17, 2002 8:24 PM
Subject: [filmscanners] RE: The"Pepper Grain" problem


> Can we now rely on those with an obsession with regard to depth
> of field on
> Nikon scanners remaining silent on that particular issue?

I don't know about that, but I believe using the term "depth of field" with
respect to this discussion is erroneous.  I posted this once before, but I
guess you missed it:

As quoted from "Modern Optical Engineering" by Warren Smith, page 156:

"The photographic depth of focus

The photographic depth of focus is based on the concept that a defocused
blur which is smaller than a silver grain in the film emulsion will not be
noticeable.  This concept also can be applied to a pixel size, for example,
a charge coupled device (CCD)."

Depth of field, as we know it in photography, is based on a "circle of
confusion", which in turn, is based on viewing distance, ability of the eye
to discern and the film format.  Depth of focus is not based on any of these
things and since scanners don't have any "circle of confusion" or "viewing
distance", associating depth of field
with them seems erroneous.

Austin

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