A bit of a rant, delete if necessary.
John Lind wrote:
> The 35/2.8 is really a 24mm lens with an image circle much
> larger than the film gate (rectangular hole where film gets exposed).
Sorry to be anal-retentive, but the 35mm shift lens *really is* a lens
with 35mm focal length. Not 24mm or anything else. Thirty five
milimetres.
A lens for a full-frame 35mm camera needs to make an image circle 43mm
in diameter -- the length of the diagonal of the film format. Most
lenses for 35mm cameras make a circle which is just big enough to cover
the film, and nothing more. The Shift 35mm is different from a "normal"
lens because its image circle is quite a bit bigger than the film
format. The 35mm shift lens allows 12mm movement maximum, so it has an
image circle of about 43+24=67mm. It is still a lens with 35mm focal
length though.
Getting a sharp and contrasty image over such a large image circle is
hard, and the retrofocus deisgn needed to fit the SLR design makes the
job even harder. Hence shift lenses for 35mm are usually ruinously
expensive, and rarely as sharp as their fixed mount siblings because
they are harder to design, and harder to make what with the moveable
mount and all.
That's why large format is ideal for this kind of stuff: there is no
reflex mirror to worry about so the lenses can use symetrical designs
(our beloved 50mm and 40mm lenses are symetrical). Symmetrical designs
are the easiest to correct, so the designers have room to either make
them fast (like the 50 f1.2) or make them cheap (the 50 f1.8) or make
them small (the 40mm f2) or make them sharp (50 f1.4?) or whatever
combination of these qualities the designer feels like.
A modest large format camera with 90mm wide angle lens will be
significantly cheaper than the 24mm shift lens alone. (90mm in 4x5 is
equivilent in angle of view to 24mm in 35mm.) If you want the Zuiko 24mm
shift lens to complete the set, then get it. If you wanna do the best
architectual photography, get large format. Horses for courses.
> With the shift, the 35mm angle of view you crop out of the 24mm image
circle ends up on a full frame of film.
Me being anal retentive again... the normal 24mm lens has *exactly* the
same image circle as any other normal lens -- 43 mm.
Sorry to rant, but the "photo teacher" in me cannot stand this confusing
and counter-productive lexicon. Forget angles of view and focal length,
think image circles. Makes it so much easier.
Vaughan Bromfield
Education Consultant
Information Technology Division
University of Technology, Sydney
Australia
tel: + 61 2 951
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