--- Pawel Nabe <[EMAIL PROTECTED]> wrote:
> 1) Why can you set 'film speed' on a digital camera?
> What does this effect?
If you set a higher film speed the camera will use a
shorter exposure time. In order to get a correct
exposure the values have to be multiplied by a certain
factor. For example assume that each color value has a
precision of 8 bits which is equal to 2^8=256. If you
integrate (collect) photons (light) over a shorter
time the output of your measurement will be
considerable lower then 256. In order not to get a too
dark picture you have to multiply the values (quite
simplified). If before you has an absolute error of 10
pixels (out of a range of 0..50) and you multiply by 5
you get an error upto 50. On the other hand if you
chose a longer exposure (lower ISO) the camera will
add photons for a longer time and the output of your
measurement gets close (or even higher) then the max
value of 256. So you don't have to multiply the
values. So if you have an error of 10 this absolute
error will not change.
> 2) The resolution of digital cameras usually heavily
> depends on the
> temperature of the CCD or CMOS chip. Do your
> pictures come out worse
> when your D30 is hot?
I think this is mainly a problem CCDs and very long
exposures. For 'normal' circumstances you probably
won't see any pratical degredation of your image.
I have to mention that I do not have any practical
experience of what I wrote here. This information just
comes from my personal interest in digital photography
and therefore could be wrong.
Robert
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