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On 12 April 2010 15:30, Oliver Tonnhofer <[email protected]> wrote:
> On 12.04.2010, at 14:34, Sebastian Haase wrote:
>> My point was also, that I would doubt that there is physically(!) more
>> information than 16e6 possible values per pixel.
>> A digital gray scale CCD camera with more than 12 bits costs multiple
>> 1000s of Euros or Dollars...
>
> Every current DSLR camera has more than 8bits per color, a Canon EOS 450D
> has 14bit for example.
That's linear bits though. Once you add a companding curve (like a
gamma) to it, you can get away with many fewer bits than that. As a
rough guide, a high-quality uncooled CCD is good for up to about 12
bits linear, or 8 - 10 bits with a gamma.
Most flatbed scanners use a line sensor with rather a short exposure
time (only a few ms) to keep the scan-speed up. As Sebastian says, you
are unlikely to be getting more than 8 bits of signal.
John
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