Re: Lifesize closeups

[T3D John Bercovitz <bercov@xxxxxxxxxxx>]

>   This using of film chips that aren't centered over
> the lenses sounds like view camera movements to me.
> So for my MF problem do I need to do the equivalent
> and move the lens 10 mm or whatever away from the
> centre of the film gate (assuming the light cone
> will still illuminate it)?

Sure it's like a shift but I accomplished the shift 
with the SLR by throwing away film at one end of the 
transparency, not by actually shifting the lens of
course.  8-)  If your MF camera has shift, like that
Fuji for instance, you can use it otherwise you have
to do it by throwing away film same as with an SLR.
A Fuji 6x7 rangefinder or Pentax 6x7 SLR will give
you lots of film to work with.  

So let's say you have an 80 mm lens on your 6x7 and
you want to take a closeup of something a foot (300 mm) 
away.

   1     1     1
   -  +  -  =  -
   s'   300    80

and s' = 109 mm

Your shot separation is 64 mm and half that is 32 mm.

(32/300)109 = 12 mm   (Hey, your 10 mm guess wasn't bad.)

So your offset in your 66 mm wide film is 12 mm.  Ergo
your maximum aperture width is 2((66/2)-12) = 42 mm
Sounds like you need one of Honest Joel's MF portrait
mounts.  They're 40 wide and 50 tall.

John B

PS: This brings up a point about closeups.  For stereos
in 5 or 7 P that you're going to project, you want 70
mm lenses as St. Ferwerda said.  That's the operating
focal length, not the length marked on the barrel.  I
have a few choices.  I can put my 35 mm lens on a 15 mm
extension tube and that will give me 50 mm to use the
pair in a Brumberger.  Or I can put it on a 25 mm
extension tube and rack it out as far as I can and get
pretty close to 70 mm (m = 1).  But this isn't a macro 
lens so I'd do better with a 55 or 60 mm Nikon lens.  
How close can I get to the object with the 55 lens?   
With the 60 lens?

   1     1     1
   -  +  -  =  -
   70    s     55

 s = 257 mm
 m = s'/s = 70/257 = .27 of life size


   1     1     1
   -  +  -  =  -
   70    s     60

 s = 420
 m = s'/s = 70/420 = .17 of life size


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