William Robb writes:
> What I would like to know is what sort of
> dynamic range in stops (a concept I do
> understand) does a CCD chip have? Is it variable
> based on software or is it hardware limited?
I have no idea. I do wonder if the in-camera exposure compensation is done
in the digital domain or if it sets the gain of an analogue amplifier prior to
sampling. The second way will result in more useable data provided you've got
enough linearity and dynamic range, and a low enough noise floor in the
analogue stage. I am of course assuming that the CCD elements are
essentially an analogue device with a DAC somewhere either on the CCD chip
itself or separately in the camera.
Another thing is that the camera firmware can always interpolate. You can
easily sample at (say) 8 bits per channel, then when you're interpolating the
extra pixels to fill the gaps left by the CCD, you can add a few bits. This would
be very similar to the oversampling process used in expensive CD players that
use 20-bit DACs.
> Is it closer to a short range slide film such as
> Velvia? Or closer to a long range print film
> such as Portra NC?
> Or is the question to general to give a specific
> answer to?
It'll depend on the CCD itself. Someone would have to try it out to be sure
(unless you want to read some semiconductor datasheets).
Cheers,
- Dave
David A. Mann, B.E. (Elec)
http://www.digistar.com/~dmann/
"Why is it that if an adult behaves like a child they lock him up,
while children are allowed to run free on the streets?" -- Garfield
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