[filmscanners] Re: IV ED dynamic range... DYNAMIC RANGE!

["Todd Flashner" <tflash@earthlink.net>]

Snip

Austin

Thanks for your other answers.

>> By your definition Dmax would be the entire density range of
>> the film?
>
> The range from the lowest density to the highest density, yes.
>
>> So is DR effectively = density range / noise?
>
> Yes.
>
>> If it were that it would be pretty easy to say so. Never seen it in any of
>> the sources cited.
>
> Er, that's exactly what I've said at least a thousand times.  If you convert
> the equation above to log, it's the same as what ISO says...since division
> in regular numbers is subtraction in log math.

Well, I mean say it literally, as in DR= density range / noise,  ISO says
Dmax - Dmin, but it does not define Dmin as density range, it defines it as
Minimum density where the output signal of the luminance OECF
appears to be unclipped. I just don't see how that is OBVIOUSLY a range.
They say it is A density, the minimum density, not a range of densities. If
it were obviously a range I think there would be no discussion here.

Note, I don't expect any of this to be "obvious" to me, but I'd expect a
simple definition to be obvious to other engineers in the field, and this is
apparently not.

> So, in log form, your equation above is:
>
> DR = density range - noise
>
> But...with transmissive density measurements, the darkest is the noise...not
> the lightest, as noise is the highest density number, and saturation is the
> lowest density number...hence, why ISO has it stated as Dmax - Dmin and in
> log math it all works out correctly.

Yes, sorry I confuse when logs are being used, etc.

> BTW, I just wanted to post a SIMPLE statement of correction to some
> misinformation posted, not get DRAGGED back into this discussion.

I know, but you know how that goes. ;-)

Todd

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