Re: Latitude and filter-behind-the-lens

[Don Roberts <droberts@xxxxxxxxxxxxx>]

So am I correct in assuming that the normal correction for IR focus will be
adequate?  Or should it be more?  Or less?  Or do I just have to experiment
based on the thickness of the filter?  I'm thinking Lee polyester here.
I may have to use gels just to get the mag to lock into place.

> Placing a filter of significant thickness behind the lens WILL alter
> the focus.
> If you put a filter, other than a wratten type, behind the lens, you
> will have to increase the film/lens distance to compensate.
> Some polaroid film backs that cannot bring the polaroid film to the
> original film plane, use a glass or plastic plate to move the plane
> of focus back to where the polaroid back places the film.
>
> > > As owner of same equipment I'm very interested in the subject you
> > forward to the List. IMHO a good quality filter placed in front of the
> > lens doesn't alter the focus. When placed behind the lens there will be
> > no alteration either. Also in your case where the filter is placed in
> > the filmback. So you still have to correct your focus for IR as usual. I
> > don't have that special 70 mm back, but I think that this also applies
> > for your back. What do others think about this?
> >
> Hope this helps!
>
> Dave Horn
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- --
==========================================================
  Don Roberts * Bittersweet Productions * Iowa City, IA
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"Ignorance is not bliss - it is oblivion." - Philip Wylie
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