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[OM] Re: SHIFTY questions

Subject: [OM] Re: SHIFTY questions
From: "Piers Hemy" <piers@xxxxxxxx>
Date: Mon, 20 Dec 2004 13:14:20 -0000
The 24 does shift horizontally.  And diagonally - as does the 35, I daresay!

A further way of looking at things shifty is to envisage what the lens does
to the subject field (never mind the object field on the film, that will be
a 24x36 rectangle).  One way of doing that would be to see what happens to a
"converging verticals" image once you have used 'Edit Transform Perspective'
in Photoshop - you get a trapezium which has to be cropped.  

Another way is to realise that when shifted vertically upwards, the subject
field becomes this shape (hoping that this survives email, but please use a
monospaced font!):
Line  1          ----------
Line  2         /          \
Line  3        /            \
Line  4       /              \
Line  5      /                \
Line  6     /                  \
Line  7    /                    \
Line  8   /                      \
Line  9  /                        \
Line 10  --------------------------

Which is also a trapezium, but doesn't need to be cropped, as it ends up a
rectangle on the film.  Once I had that clear, it was obvious to me that a
shift lens is not just for architectural images.  See my last TOPE entry,
for example, which has pretty much no verticals at all, yet could not have
been done without a shift lens.

--
Piers 
 
-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
Of Andrew Gullen
Sent: 20 December 2004 13:01
To: olympus@xxxxxxxxxx
Subject: [OM] Re: SHIFTY questions

on 2004/12/20 5:33 AM, jking@xxxxxxxxxxxxxx at jking@xxxxxxxxxxxxxx wrote:

> Next on the list to feed by addiction... shift lenses... but not till 
> next year... :-))))
> 
> How do they work?
> 
> Does the lens correct perspective when the camera is in landscape 
> orientation and also correct when I take tall buildings in portrate 
> orientation?

If they shift horizontally and vertically, then they work both ways. The 35
shift does and I'm pretty sure the 24 does too.

The lens shifts sideways. This allows you to keep the back of the camera
parallel to whatever you're shooting so perspective doesn't get distorted.
You shift the lens up (for example) to look up towards a building.

An easier way to understand what's going on is to think of holding the lens
still and shifting the camera. The lens makes a large inverted image (larger
than the 35mm frame), so you're shifting down to get some piece of the lower
part, which is the upper part of the scene.

Andrew


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