Re: Halo effects (was: Re: Maco IR 4x5)

[Marco Pauck <pauck@xxxxxx>]

George L Smyth wrote:
> > Eckhard Stephan wrote:
> > [...]
> > > Besides that, I would like to have at least SOME halos...
> >
> > How about putting a Zeiss Softar (or a poor man's version avialable
> > from other manufacturers) in front of our lens?
> >
> > Halo effects have nothing to do with infrared effects (such as
> > white foliage). They are just 'incidentally' both separate features
> > of Kodak's HIE. It would give us more freedom if we could control
> > each of the effects separately depending on the subject.
> >
> > Sensitivity to the infrared part of the spectrum is a feature of
> > the emulsion, i.e. the film. Halo effects should be limited to be
> > a feature of the optical system, i.e. the lens!
> 
> The "halo" effect is due to the lack of an anti-halation layer.  The light
> passes through the film, strikes the back plane, then goes back through the
> film, reexposing it.  Using a lens to try to do this won't come close to
> being the same thing.

Well, of course the *physical background is different*: for HIE it's
mainly light scattering due to the missing anti-halation layer and
for a lens with defocus control it's spherical aberration that places
a secondary defocused image over the sharp primary image.

However, I guess that the *results are quite similar*: a halo which
is especially visible around bright subjects such as light sources.
Maybe not identical but so similar that it doesn't compensate for
the limited flexibility due to having the halo effect 'built-in'
without any choice.

Anyone with a DC lens or a Softar to give it a try?
I.e. shoot some subjects with both HIE without and Konica or MACO
with DC/Softar and compare the results. (Probably Kodak Recording 2475
will also be a good non-IR substitute for HIE as it has similar grain.)

Also note that there are different approaches to soften an image.
Some (e.g. the famous vaseline) primarily just reduce contrast.
Only 'true' DC lenses and the Zeiss Softar will count!  ;-)

	Marco
-- 
Marco Pauck - WMD GmbH Hamburg, Germany - http://www.pauck.de/marco/
e-mail: marco@xxxxxxxx, phone: +49-40-58958-120, fax: +49-40-58958-199
For every complex problem, there is a solution that is simple, neat,
and wrong.  -- H. L. Mencken
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