Re: Effects of lens length

[P3D Bob Wier <wier@xxxxxxxxxxxxxxx>]

>>> question -
>>> if you crop an image taken with a 50 mm lens to the same part as
>>> an image taken with a 80 mm lens, and make them the same size - would
>>> you have the same thing as two pictures both taken with 80 mm lenses?
>>> 
>>No. The length of a lens impacts the relationship of foreground and 
>>background objects.
>
>Sorry Marvin, but I think the answer is "yes".  The FL will only affect
>the magnification. If you are standing at the same spot then you can
>magnify or reduce pictures taken with different FLs for perfect match.
>BUT, if you move to match the field of view of the two lenses, then
>you have altered the perspective or, as you say, the relationship of
>foreground and background objects.
>
>It's a simple concept and yet not many people get it right.
>
>George Themelis

Now that I think about it, I believe George is correct. The effect
in "Vertigo" was created by moving the camera position, and adjusting
the zoom factor to keep the actor's image the same size. The actor/
background relationship change was due to the change in camera position
rather than the change of "zoom".

The effect I'm thinking of would be holding the camera position 
essentially the same (separated by stereo spacing) and only changing
the "zoom" factor. In considering what I see when I do a zoom with
my 25 - 80 SLR lens, the images gets larger or smaller, but
it does not change the spatial relationships within the frame itself.

At least, as best as I remember...

THANKS

  -------- Bob Wier ----- wier@xxxxxxxxxxxxxxx -----
          Friday, August 30, 1996  1:21:27 PM
          Texas A & M University - Commerce
   keeper of the Motorola MC68HC11, ICOM Radio, and
 Overland-Trails mailing lists and the LDS Genealogy
            State Research Outlines 



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