On Jul 22, 2005, at 12:42 PM, Cory Papenfuss wrote:
Is there any technical reason why one couldn't build a high-
quality optical converer to go between a DSLR body with 1.5x crop
and an full-frame lens? The telephoto end of the lens spectrum is
pretty easy to fill with old glass, but the wideangle and fast
normal is pretty difficult. I just bought an SMC-M 50/1.4 and an
SMC-K 50/1.4 for my -DS and I *love* the speed, sharpness, and
bokeh. What I don't like is the effective 75mm FOV.
I just don't understand what is so difficult ...
DA18-55 = FOV 28mm to 82mm on 135 format
DA16-45 = FOV 24mm to 60mm on 135 format
FA20-35 = FOV 30mm to 50mm on 135 format
For primes, a DA14mm f/2.8 is a fast ultrawide; an FA35/2 is a good
fast normal; a FA31/1.8 is also a good, fast normal; an FA*24/2 is a
fast wide.
What's the big difficulty?
For lenses designed with large image circles, it would seem that a
wideangle converter between the lens and the body could collect the
*entire* circle of light projected onto the film plane and preserve
the FOV and aperture of an 50/1.4 on a DSLR.
Any rear-mounted "wide converter" is going to cost resolution, speed,
and rectilinear correction, never mind making the lens assembly much
bulkier and heavier.
Godfrey
