Toralf Lund wrote: > Eric Featherstone wrote: > >> On 06/07/06, Toralf Lund <[EMAIL PROTECTED]> wrote: >> >> >>> I was talking about the number of different voltage levels that may be >>> output from the sensor itself. That number is not necessarily 4096; it >>> is the analogue-to-digital converter that has 4096 different values. >>> >>> >> Toralf, the sensor is an _analogue_ device, of course it produces more >> than 4096 voltage levels. It produces an _infinite_ number of levels >> >> > I'm afraid not. A CCD can only output a certain set of distinct voltage > levels. I think Godfrey explained this earlier. I should perhaps add that there are at least two different factors that come into play here. One is the actual charge at the photo site - which can only take one of a certain number of discrete levels (i.e. it is not a continuous range), the other is the electric noise in the system. Adding noise to the system essentially means that you will no longer be able to tell nearby charge-levels a part, thus reducing the number of usable output "values".
I'm not sure *exactly* what the numbers are in today's DSLR sensors, but I don't think the final figure can be that much higher than 4096. I was speculating that it might be, say twice as large or 4 times as large. But maybe they don't dimension the systems that way; perhaps the fact that a 12-bit A/D was chosen actually indicates that the number close to 4096, or at least significantly smaller than 8192. And again, I certainly think that the actual relations here has impact on the exposure considerations we are discussing. - Toralf -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
