[filmscanners] RE: Density vs Dynamic range

["Austin Franklin" <darkroom@ix.netcom.com>]

Ei, Robert...good man!

> Here is a link to the standard proposal:
>
> http://www.pima.net/standards/iso/tc42/wg18/ISO_21550/N4909_WD21550_v3.PDF
>
> Since it is just a proposal comments can be submitted to:
>
> http://www.pima.net/standards/iso/tc42/wg18/ISO_21550/WD21550_Comm
> ent_Form.d
> oc
>
> I would appreciate your input on that.

I'm concluding they are saying the EXACT same thing...  Simply put, they
have dMin as the noise floor, and dMax as the clipping point...all correct,
and remember, it's in log values (they specifically say density
value...which is a log scale).  Subtraction in logs is the same as division
in "regular"...

ISO equation -> dMax - dMin:

So, for a dMax of 3.6, and a dMin of .2 -> 3.6 - .2 = 3.4


the Dynamic Range equation out of "Digital Signal Processing in VLSI":

DR (dB) = 10log10(largest signal/smallest discernable signal) or:

3.6 is equal to 10**3.6 or 3981, and .2 is 10**.2 or 1.5849...

SO...

DR (in Bells, not DECI-Bells) = log10(3981/1.5849)

Which, is 3.4 ;-)

So, it appears they are saying the exact same thing.  Any comments?

Regards,

Austin

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