Re: Photo Image out of focus

[Larry Cartwright <exit60@IA4U.NET>]

> Jeff Weitz wrote:
> Is anyone on this list a knowledgeable photographer who can resolve
> this question one way or the other.  I'm not sufficiently aware of the
> optics of the development process to answer directly.  Is there an
> optical solution to the focus problem?

The short answer is:  no.

One of the first things I learned from darkroom experiences is that
printing and enlarging is not going to be able to bring an image to a
sharper focus than exists on the negative.  I think we all start out
with a not-very-well-thought-through faith in symmetry which has us
convinced that anything which can be done can somehow be undone by
reversing the process.  After all, image *size* is symmetrical and
reversible, and we can make images lighter and darker and play with the
colors.

It doesn't take too much experimenting to shatter the focus delusion.
You quickly find that the enlarger can make the image even more *out* of
focus, but there is no purely optical way to make the image more *in*
focus than it is on the negative.  Not even with all the king's horses
and all the king's men :-)    [I don't thinks it's technically an
entropy example, but it acts like one.]

The darkroom process is classic converging lens optics with a "real
image" produced.  If you do some ray diagramming you soon see why a lens
can't reconstruct a sharp image from a blurred negative.  With purely
optical 2D rendering, the best you can hope for is an accurate rendition
of the immediate source.  It is truly a "garbage in, garbage out"
process.

Best wishes,

Larry

~~~~~~~~~~~~~~~~~~~~~~~
Larry Cartwright
Retired Physics Teacher
Charlotte MI USA
<exit60@ia4u.net>
~~~~~~~~~~~~~~~~~~~~~~~