Julian
This sounds like an amazingly lucid explanation. Thanks for clarifying that.
I know I've looked at a lot of audio references and have yet to see a
"density range" specification within them. Electrical components just don't
seem to have density ranges, they have dynamic ranges, which is a
description of the range of power levels they can reproduce cleanly. Things
that block or reflect light have density ranges, and a scanner's DyR is a
quantification of the density range it can READ, but electronics in and of
themselves just don't have density ranges.
Is it fair to say that any item that LITERALLY has a density range can not
LITERALLY have a dynamic range, and vice versa? I'd think so! I'd think an
item could have a density range and a resolution, or a dynamic range and a
resolution, but it can't have a dynamic range and a density range and a
resolution...
Todd
> At 14:53 30/08/02, David wrote:
>> Does that mean you claim that density range and dynamic range are equivalent
>> measurements of the same physical quantity?
>
> Well yes and no. Density range is normally a property of a slide or piece
> of film, or an image on a film. Dynamic range is normally a property of
> some processing device, like a scanner in this case. If you have a slide
> that can just be scanned by a scanner without the scanner saturating or
> getting the black bits lost in the noise, then the slide's density range is
> the same as the scanner dynamic range, in that case.
>
> A scanner doesn't have a "density range", but it has a range of densities
> that it can handle. The maximum range of densities that it can handle in a
> single pass is its dynamic range. The maximum range of densities that it
> can handle under any circumstances is it's "static" range, or max range,
> sometimes called just Dmax by manufacturers. (Inaccurately, but we think we
> know what they mean. Dmax is not a range, it is a figure. When they say
> this, they are by implication assuming an upper limit of 0dB as the other
> end of the range).
>
> So if a slide's density range is greater than the scanner dynamic range
> then the scanner cannot capture the whole density range of the slide.
>
> I am using the terms as they are normally used. Both are measures of range
> of densities. One is the range of densities actually or potentially on a
> slide, one is the range of densities that a scanner can handle.
>
> You *can* talk about the "dynamic range of a particular slide" and be kind
> of correct. Or you could talk about the dynamic range of the medium (that
> is, the particular film). Dynamic range is, as it always has been, nothing
> more than the range of largest signal to smallest signal, usually expressed
> as a ratio. On an actual slide it is easy enough to pick the largest
> signal (the lightest density) and the smallest signal (the densest area
> which is just discernable against unexposed film background). For the
> medium, the relevant figures are the lowest POSSIBLE density, and the
> highest POSSIBLE density that can still be discerned from background
> black. If you use the language this way, then the slide's dynamic range is
> the same thing as its density range.
>
> Julian
>
>
> Julian Robinson
> Canberra, Australia
>
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