Re: Effects of lens length (and "something else")

[P3D Michael Kersenbrock <michaelk@xxxxxxxxxxx>]

> > No. The length of a lens impacts the relationship of foreground and background
> > objects. There is a famous shot in the movie Jaws (which has been copied 
> > 
> On the contrary, this example does not apply because the distance from the
> camera to the subject changes. The point of view is what matters. More later
> if someone does not believe me.

George is quite right.  It's a classic 2D photo class thing.  Perspective is
set by where the photo is taken.  Lens focal length (or zooming...) is a
front-end cropping/framing-like sort of activity.  The classic example is 
comparing a telephoto picture of a person's face and a "normal" lens picture
of the same person from the same place -- but the image enlarged/cropped to the
same size as the telephoto one.  Same picture perspective-wise.  This is why
I was taught to *move* to create images -- and why some didn't like beginners
to use zooms, at least in the days when zooms weren't so popular.

The thing that gets missed is that for a *given* size subject image in the camera's
viewer, if one changes focal lengths, one *moves* to "compensate", but that moving 
changes perspective.  They say that for 35mm photography that 105mm lenses are good
for portraits because it flatters the subject... it's not the lens length, it's the
distance the longer lens "forces" one to use that does the flattery.

On a related subject in a related thread (my actual subject but the prior two
paragraphs are good lead-in).... *because* of the forced-moving effect in the last
paragraph,  the original question that someone asked about whether the cameras
should be spread further apart if telephoto lenses are used is probably answered
'yes' from a pragmatic point of view.  What I mean is that *if* one is using
telephoto lenses, then *probably* the central foreground focal-point subject is 
far away, and therefore a wider separation is likely desired to gain 3D'ness.  
So technically, the separation is based on subject distances (and effect 
wanted) but that distance is often linked to focal length of lenses used
(but not always!).

Mike K.


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