[filmscanners] Re: Depth of Focus (was Nikon LS-40 vs PolaroidSS4000)

["Arthur Entlich" <artistic-1@shaw.ca>]

Anthony Atkielski wrote:

> Does this depth of field problem affect mounted 35mm slides, too?
>


 From discussions previously, it would appear to.  Some people suggested
using specific types of slide mounts which minimized the problem (not
necessarily glass ones either).

My Kodachrome slides from years ago have a very obvious concavo-convex
form to them.  This was back when they seemed to use a slide mount with
a internal rectangular embossing, which might have been done after the
slide was mounted.  Older paper mounts used a thermal glue all the way
around the image, causing the image to tend to peak in the middle quite
a bit.  More recent mounts are either free-floating or only physically
attach to the slide on one edge, which allows for expansion and
contraction without so much buckling.  This reduces "popping" in the
projector as well (where the image suddenly changes focal position, and
has to be refocused).  Many slide projectors preheat the slide to help
prevent this by pre-popping the film.

Anyway, yes, there were complaints about the DOF problem with some slide
mounts.

Art


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