Hi Dan,
As I understand it; and being a long-time spectacles-wearer, I have some
first-hand experience in the matters since the effects are similar.
Particles of black or dark-grey dirt have no reflectivity. They don't scatter
any
of the light on the way to the film. So if there are only a few they will stop
some (a tiny bit) of light from reaching the film and doing its work, and
that's
all. You will never notice the little bit that is not there.
However, fungus (especially on the rear lenses) (fungus is white or light-
coloured), a film of grease, mist, anything white or light-coloured, reflects
the
light. Scatters it about. Reduces contrast and also sharpness. Take a pair of
spectacles and huff on them, then try looking through them and see what
you get.
Just as in a Softar filter or putting a stocking net over the lens. Fine if you
want it, but if you don't ... ... $0.02
Brian
> > If it's black dirt, I'd just leave it Should make hardly any image
> > difference.
>
> I'm always confused by this sort of advice -- I've seen lenses for sale
> that say "dirt on lens, but doesn't affect the image", or even lenses with
> chips being described here as usable.
>
> How can this be? If something's right on the surface of the lens presumably
> it's not going to be in focus, so I get the basic idea -- but if so, why does
> anyone bother cleaning lenses? How dirty can a lens get before the change is
> visible? (well, I guess this depends on how large you want to make the final
> image, film quality, etc, etc, but in general?)
>
> -- dan
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|