[filmscanners] RE: scanner dmax discussion

["Chuck Cole" <cncole@earthlink.net>]

> -----Original Message-----
> From: filmscanners_owner@halftone.co.uk
> [mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Paul D. DeRocco
> Sent: Thursday, July 17, 2003 4:57 AM
> To: cncole@earthlink.net
> Subject: [filmscanners] RE: scanner dmax discussion
>
>
> > From: filmscanners_owner@halftone.co.uk
> >
> > No: decades as in 90dB power range... ten to the ninth power.  An
> > octave is
> > only a factor of two...  1::512 is very much smaller.
>
> But a photodiode, given 9 decades of light range, produces 9 decades of
> current, not 9 decades of power into a resistor, so that would be
> 180db, not
> 90db.

The optical power range on the photodiode producing the current is 90dB.
The electrical dBs aren't usually used.  This is always confusing because
the photodiode converts optical power directly to current so the current
ratio is equivalent to the input power in this case (  .65 times optical
power is the signal current ).

>
> --
>
> Ciao,               Paul D. DeRocco
> Paul                mailto:pderocco@ix.netcom.com
>
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