on 8/29/02 2:26 AM, David J. Littleboy at davidjl@gol.com wrote:
>
> Todd,
>
>>>>>>>>>>>>
> My primary point was that with DyR defined as Dmax - Dmin, as it is by the
> ISO, it is the range between the minimum discernable signal (which is what
> the ISO calls Dmax) and the maximum signal before clipping (which is what
> the ISO calls Dmin). Period.
> <<<<<<<<<<<
>
> But what do you mean when you say that "dynamic range is a range"?
>
> Dynamic range is _always_ a ratio. If it's not, it's something different.
> For example:
>
> "ISO DSC dynamic range
> ratio of the maximum luminance level that appears unclipped to the minimum
> luminance level that can be
> reproduced with an incremental signal to temporal noise ratio of at least 1,
> as determined according to ISO 15739."
>
> df
>
> In the definition you quote above, "Dmax - Dmin", Dmax and Dmin will be log
> values, and thus the expression "Dmax - Dmin" _is_ a ratio. (I suppose these
> should all be "Dmin - Dmax" <g>.)
>
David,
I can't figure out why you and Austin have such a mental block about
ranges and ratios. In all the situations we're talking about, they are
just plain one and the same. Dynamic Range is a ratio AND its a range --
that's why they call it a range! Similarly, Dmax - Dmin is a ratio and
its also a range -- looks like a density range (a range as well and its
a ratio). They are ALL the same kind of animal.
Todd is reading and interpreting the ISO standard and that audio paper
entirely correctly. Listen to him.
Roy
> David J. Littleboy
> davidjl@gol.com
> Tokyo, Japan
>
Roy Harrington
roy@harrington.com
Black & White Photography Gallery
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