More Sputnik Focus Tips (from my archives)

[Stephen Puckett <spuckett@xxxxxxxxxxxx>]

Date: Fri, 17 Apr 1998 02:06:57 -0400
From: Brian Reynolds <reynolds@xxxxxxxxx>

Joel wrote:
>
> Introducing Tony Russel, who I've just added to the list.
> Tony shoots using a Sputnik, and I added him to the list
> as he has this question I think you more handy than I can
> probably answer:
> 
> 
> > I have used a Sputnik for some time now and would recommend it to 
> > anyone, but having read your shutter adjustment article, I thought 
> > you may have some idea how to handle a problem that I have.
> > My left hand lense (looking from behind) is slightly out of focus.
> > How can I release the gearing to refocus the lense, and if I manage 
> > to release it - how should I go about focussing the lense before 
> > locking it back into place?.
> 

Probably the easiest way to check focus is to mount the camera on a
tripod, open the camera back and put a piece of ground glass (or
frosted Scotch tape in a pinch, but be careful about getting adhesive
from the tape on the film rails), frosted side towards the lens,
across the film guides.  The glass should rest right on the rails that
the film moves along.  35mm cameras often have two sets of rails, the
inner pair are what the film runs along (and what you want the ground
glass to rest on) and the outer pair (which are thicker than the inner
pair) guide the edges of the film and keep it running straight.  I
haven't seen the inside of a Sputnik, so I don't know what the rails
look like.

Put a dark cloth over the camera (stretch the neck of a black sweat
shirt around the camera and put your head in the body of the sweat
shirt) and focus on a distant object while examining the ground glass
with a loupe (or other magnifying device).

If you're really dedicated you'll do this at night and focus on a star
to get infinity focus.  The truely fanatical cut a bevel in a film
chip (about the size of a thumb nail) and glue it to the frosted side
of the ground glass so that the edge of the bevel is off the ground
glass by the thickness of the film.  This forms a knife edge, which
allows for very precise focusing.  By sweeping the camera in azimuth
(sort of, it's probably actually Right Ascension) the edge of the film
bevel will cut the cone of light formed by focusing star light on the
ground glass.  If the image of the star blinks out all at once you are
in focus, otherwise the image will gray out from one side to the other
(the direction depends on whether you are inside or outside of focus).

If you don't want to wait until night, and are somewhat handy, you
could build a (auto)collimnator to use as a substitute for a star as a
target at infinity.  Sam Brown's "All About Telescopes" from Edmund
Scientific explains how to build one, and about knife edge testing for
focusing.