(OT) Cameras in low light

[Peter]

Lennart Sorensen <lsorense at ...> writes:
> NO, it certainly is NOT all in the glass.  The lens is very important,
> but a sensor with 2 or 3 times the surface area will receive more light
> and _should_ be able to handle lower light conditions.  There is
> apparently also difference in sensor technology (CMOS, CCD).

fwiw sensor pixel storage capacity (dark pixel) has been measured in a few
(10-100) electrons for quite a few years now. There are no easy shortcuts to
improve that. 10 electrons in a pixel well + Heisenberg means a certain
guaranteed noise no matter what one does. So the 'glass' is very important, but,
counter-intuitively, the best lenses for low light are those with *few*
elements, and not the super duper zoom lenses sold with DSLRs. Keep in mind that
even large telescopes (refractors) have only 3 or 4 lenses in the light path. A
modern zoom lens has in excess of 8 and sometimes 12-14 lens elements. At every
air/glass interface light is lost, in despite of antireflex coatings. Occam's
razor works perfectly here too. From the light transmission point of view a
super duper zoom is likely under 50% efficient, maybe more, where a single thin
lens can pass 95-98% of the incident light. Simple = best bang/buck. Then with
low light one uses a large aperture and long exposure, with the result that
non-static objects are unsharp, and static objects are only sharp in the narrow
range set by the depth of field of a wide open aperture (just a few cm at best
anywhere closer than infinity). So there are no shortcuts really. My current
favorite is essentially a cheap pinhole lens (well not really, but fixed focus
3.8mm lens with fixed aperture at f/8 or so). Makes for great photos as long as
one does not enlarge them afterwards. Oh, and don't get me started about using
autofocus in the dark (did that multiple flash red af led scare everyone off
yet, so they are blinking and turning away, or are they waiting for the preflash
to comb their hair). So, dark = simple lens, no flash, good sensor, and don't
expect miracles, because they are few and far between.

Peter


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