Chris Malcolm <cam@[EMAIL PROTECTED]
> wrote:
>In rec.photo.digital Mr.T <MrT@[EMAIL PROTECTED]
> wrote:
>>> I suspect you may be confusing resolution with range. The problems you
>>> refer to are problems of range.
>
>> Did anyone mention resolution, can't see it in this post myself.
>> (other than your latest "input")
>
>The connection between number of encoding bits and resolution of the
>resulting encoding in analogue to digital conversion is probably
>something else your photographic education omitted. If so then you
>wouldn't have realised that you were the one who brought it up by
>suppposing that the number of encoding bits in the camera sensor
>affected dynamic range. It doesn't. Any number of bits can encode any
>dynamic range you like. What the number of bits affects is the
>resolution with which that dynamic range is encoded.
Your description is incorrect. The sensor is analog, it
has no such thing as a "number of encoding bits". The
digital to analog conversion is not integral to the
sensor, and of course the analog output from a sensor
has a known dynamic range; however, while the number of
bits, e.g. 12 or 14 are now common, does not determine
the dynamic range of the sensor output, it can and
sometimes does limit the dynamic range of the resulting
digital signal (e.g., when the dynamic range of the
digital format is less than the dynamic range of the
analog output from the sensor). I.e., no matter what
the dynamic range of the sensor, the *maximum* possible
dynamic range for a digital signal is limited by the
number of bits/sample to (6.02 * N) + 1.76 where N is
the number of bits.
Suggesting that "any number of bits can encode any
dynamic range you like" is indicates that you *still* do
not understand the significance of digital technology.
"The resolution with which that dynamic range is
encoded" is no different than saying "the distortion
generated by encoding", which is exactly what *limits*
the dynamic range. In essence, quantization distortion
increases if the step size increases.
>There is a tendency for technology to progress on a number of fronts
>at the same time. Hence there has been a tendency for improvements in
>dynmanic range to accompany improvements in encoding resolution, just
>as improvements of dynamic range have also been accompanied by
>improvements in battery capacity and optical zoom ranges. But there's
>no necessary connection between them.
The fact is that as the dynamic range of the analog
sensor has increased, camera manufacturers have
progressed to using more bits per sample in order to
retain, in the digital signal, the dynamic range that
exists in the analog range. You are suggesting that 14
bit ADCs were not available 10 years ago when digital
cameras were moving from 10 bit to 12 bit ADCs. That is
not true. While certainly there have been improvements
in 14 bit ADCs over the past 10 years, it is a fact that
if CCD sensors had required 14 bit ADCs ten years ago,
they would have been used. 14 bit ADCs were not used
until the dynamic range of the sensors improved to
greater than what a 12 bit ADC can provide.
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@[EMAIL PROTECTED]
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