Digital Camera Dilemma - Depth of field

[Kenelm Philip]

	Clay Taylor just said:

>   Please remember the point of my original post - the focal length of the
> lens and the format size of the sensor (whether film or CCD) are not the
> important factors in depth of field - the magnification of the image and
> the aperture (f/stop) of the lens are.

_All_ of these quantities are important factors. It is still true that, for
the same size print, a digital camera image taken at, for example, f/8, will
have greater depth of field than a 35mm image taken at f/8, which image in
turn will have a greater depth of field than a 4x5 camera image taken at
f/8.* The 4x5 print might be a contact print, the 35mm print would be an
enlargement, and the digital camera print would be a rather large enlarge-
ment from the size of the CCD--but so what? People just don't work with
CCD-sized images! In many cases the final print size is almost independent
of the negative, or CCD,  size--especially if you are after approximately
life-sized prints of butterflies. :-)

	As for the vexed question of resolution, a megapixel digital camera
has enough resolution for publishable life-size images of butterflies. In
fact, I have seen published butterfly images taken with a 640x480 pixel
digital camera. They're not quite as detailed as film images on the same
page--but they're usable for ID.

* That sentence assumes 'normal' lenses for each camera.

	Even Ansel Adams, who knew a bit about photography, commented that
"The 35mm size (usually with a lens of 2-inch focal length) gives a greater
depth of field, even at fairly large apertures; with 35mm or 28mm lenses
the depth of field is exceptional." [Camera & Lens: Basic Photo 1] He was
comparing 35mm cameras to 4x5 to 8x10 (and larger) view cameras, but the
same principle holds going from 35mm to even shorter focal length lenses
as in most (but not all) digital cameras.

							Ken Philip
fnkw at uaf.edu




 
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