Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Jeff Medkeff <medkeff@g...> 
wrote:
> 
> 
> Roy Harrington wrote:
> 
> 
> > Seems to me this would imply an exponential relationship between the
> > light energy input and the digital values from the A/D.   But I thought there
> > was a linear relationship from the photon energy to the voltage out to the
> > raw A/D values.
> 
> It depends on how you define "brightness." But you are correct, these 
> sensors are (nearly) linear. My account is an oversimplification meant 
> to introduce the concept of dynamic range in a scene being defined 
> according to incidence.
> 
> --
> Jeff Medkeff
> Eagle River, Alaska

Ok.  I think it's interesting to note that it is specifically the mathematics of
the linear A/D data representing the ratio of the dynamic range 
that gives rise to the need for more bits to get more dynamic range.
E.G. with a 12 bit integer value the biggest ratio you can represent is 4096/1.
If you want a larger dynamic range ratio than 4096 you have to have more bits.

Roy