>From: "C.H.Ling" <chling@xxxxxxxxxxxxx>
>From: "Jan Steinman" <Jan@xxxxxxxxxxxxxx>
>
> > Not really. In raw mode, some digicams will give you 10 bits --
>essentially 10 stops. Drum scanned Velvia will yield 36db of dynamic
>range -- about 14 stops.
>
>I think 36db is a wrong value, most agree slide has D-Range of roughly 4.0,
>which is 10000:1 and 80db.
Might you be confusing voltage (or current) ratio with power ratio? Light
intensity is always expressed as a power ratio.
Each power increase by a factor of 10 yields another 10 decibels, or another 1
point of dynamic range. Thus, a 10,000:1 power ratio is 40 db, or a Drange of
4.0.
If one were measuring potential or flow (voltage or current), one would have 20
decibels for each 10x increase.
Good drum scanners can see a Drange of 4.0, but in my experience, Velvia
doesn't stretch nearly that far. On my ColorGetter Falcon, 4"x5" RVP (Velvia)
seems to run from 0.16 to 3.4 or so.
--
: Jan Steinman -- nature Transography(TM): <http://www.Bytesmiths.com>
: Bytesmiths -- artists' services: <http://www.Bytesmiths.com/Services>
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