[filmscanners] RE: Terms used in Dynamic Range calculations...

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

> > From: Austin Franklin
> >
> > The dynamic range equation is, using these terms, and the
> > provided diagram, can be either of the following:
> >
> > DR (dB) = 10log10 (largest/smallest)
> >
> > DR (dB) = 10log10 ((maximum signal level - minimum signal level)
> > / smallest)
>
> For large ranges, these are essentially the same, but the first one is
> correct, and the second one doesn't make sense. If the maximum
> signal level
> was only twice the minimum, then the second formula would call that 0db
> dynamic range.

Hi Paul,

I don't understand your comment.  Both equations are identical, as:

"largest" from the first equation is exactly the same thing as "(maximum
signal level - minimum signal level)" from the second equation.  "largest"
in the first equation is typically a "derived" term, derived from "(maximum
signal level - minimum signal level)"

If you viewed the diagram I provided, as it showed visually what the terms I
used meant.

If you have a max signal level of 10 and a min signal level of 5, that is an
absolute signal level of 5, which is the same thing as would be used for
"largest" in the top equation.

I can only guess you are confusing the terms used "minimum signal level" and
"smallest", as they are not the same thing, as I believe my write-up should
clearly state.

Your example of maximum signal level being twice the minimum signal level
does not say what noise is...and noise ("smallest") is the divisor for both
these two equations.

Regards,

Austin

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