At 07:45 15/01/01, Pete wrote:
>All the available CCDs on the market today are limited to a dynamic range of
>5000:1 (~12 bits) at normal temperatures.
Aha! That is the figure I was wondering about. Thanks so much for this
useful and factual piece of info. Given the physics I would guess that
noise figures are already towards thermal limits (?)and if so it is not
possible to do much better without cooling. So I guess too that drum
scanners etc must use photomultipliers or something other than CCDs.
But we don't know whether the new Nikons do or don't use split exposures -
which seems to be the logical way to go for CCD scanners - and should be
easy for Nikon to implement given LED sources. Maybe they do?
And probably they don't looking at the fast scan times. Multiple exposures
would significantly add to the scan time. I wonder if they have considered
this as a slower option. And then I wonder why, when they already do
multi-passes to reduce noise as in the LS2000, why they don't up the
exposure for subsequent scans? Maybe it is hard to keep things linear?
Just thinking aloud,
Julian
Julian Robinson
in usually sunny, smog free Canberra, Australia
