Winsor Crosby wrote:
"Isn't there some conventional wisdom that the larger the sensor the
less digital noise? There was also something somewhere that the
reason that Nikon and Canon were using the large sensor, besides
preserving peoples' lens collections, was that no one has figured out
how to design an ultra wide angle for a small sensor yet? So anyone
used to shooting with a 21mm would be out of luck with a small sensor
camera?"
It's certainly true that a large sensor with large pixels will have
a lower noise level. Or to put it another way, shadow detail will
not be swamped by noise, and the equivalent film speed can be higher
for the same reason. It's all down to how many photons can be
collected, compared to the 'false' signal generated within the
sensor itself.
I don't know any reason why one couldn't design a super wide angle
lens for a small sensor. But I would make some technical
observations regarding apertures.
First, there's the mechanical difficulty of making nice round small
dimension apertures for the short focal lengths, and making them
stop down consistently when the photo is taken.
Second there are diffraction effects from small apertures. Even a
standard 50mm lens is said to be diffraction limited from about f/8
down. This due to the absolute diameter of the aperture, not its
relative diameter (f no.). So small, short focal length lenses will
hit diffraction limits at wider f numbers.
Third, there is depth of field. Because you are scaling down the
camera relative to the real world, for a given f stop, the depth of
field will be larger for a small sensor system than its equivalent
lens/aperture in a large sensor system. We see the same effect in
reverse going from 35mm to larger formats - you need to stop down
more to get the same depth of field.
This great if you're into landscapes, but not if you are into portraiture.
If Olympus marketed a digital camera with physically small bodies
and lenses, that could perform as well as 35mm film, would I buy it?
You bet your Asahi.
Chris Barrett
Malvern
- --
Chris,
Would there be more diffraction softening at smaller F-stops with a
downscaled format a physically small aperture? F64 is usable with
large format, but it would just be a soft blur with 35mm.
--
Winsor Crosby
Long Beach, California
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