On Tue, 28 Jan 2003 15:55:54 +0000 (UTC), glhansen@steel.ucs.indiana.edu (Gregory L. Hansen) wrote:

>In another thread I quoted an abstract of an article that explains the

>spherical and irregular aberrations in the human eye increase the depth of

>field at some cost in acuity.

>

>That had me wondering, is there any such thing as a camera lens with

>aberrations purposefully built into it for an increase in the depth of

>field? Would there be any use for such a lens? Maybe for very long

>telephoto with wide aperture, for instance. I've seen pictures of animals

>where the face was in focus, but the fur farther back on the body was not.

>Maybe some aberration but a larger depth of field would make a more

>pleasing picture.

I have never placed the Nikkor 500mm f8 (f8 1/2 in

practice, earlier-type) next to a standard-design

500mm lens shot at f8 1/2 for comparison, but the

Nikkor mirror, with its hard-edged and complex-looking

out-of-focus area imaging (otherwise known as "bad

bokeh"...;-) and "doughnuts" does appear to have more

DOF than one would expect from a 500mm, with areas

that would normally be expected to look soft in the

image retaining a sense of detail and focus - and it

is often possible to take photos with it that appear

to have deep DOF, as when shooting a building face

at an angle, or a distant patch of ground, etc. I

once shot a series of building details (from tiny to

very large) with the Nikkor mirror for a couple of

magazine articles - and almost all the images appear

to have universal DOF, regardless of the shooting

angles... I've also noticed with other lenses with

"bad bokeh" that achieving the appearance of universal

DOF (particularly with good "crispness" on the far

side of focus) is easier...