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From: Paul Furman on 22 May 2010 19:19
Henry Olson wrote:
> Paul Furman wrote:
>> Russ D wrote:
>>> They have larger f/ratios available at long focal-lengths. They don't need
>>> larger apertures at long focal-lengths because they use smaller sensors.
>> Right, because they don't capture much light and can only make small prints.
> 1) 735mm (EFL) @ f/3.5 ISO 200 is an identical exposure whether it be done
> on a small sensor or a large sensor. Both exposures on both cameras will be
No, the P&S will have more noise and less dynamic range at ISO 200. It
is optimized for something more like ISO 50 to make clean images that
can be enlarged. There is no free lunch; you can't capture less photons
and make the same big print.
> 2) YOU CANNOT GET A 735MM F/3.5 LENS FOR *ANY* DSLR.
True, although I've got a 500mm f/4.5 with the same field of view on
AP-S. Or for FX, stacked teleconverters on the 300/2.8, which is 840mm
f/8 and push the ISO to 1600 for the same exposure.
> 3) Size of print is only limited by resolution, not by lens focal-length
> nor aperture.
Aperture does limit the resolution of P&S. P&S can't do 21MP at f/3.5,
more like a couple megapixels for smaller sensors. The smallest point
the lens could transmit at f/2.8 is about 4 microns, which for a 1/1.8
sensor would be about 3 megapixels. Simple laws of physics. A full 35mm
sensor at f/2.8 will support 60 megapixels.
> Many P&S cameras equal or beat the resolution from many
Some kit lenses are outperformed by some P&S, that's true. They still
work better in low light though.