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

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

Oops, following Austin's lead, I transposed Dmax and Dmin too!

Todd


>> I do not see ANYWHERE where it says dynamic range is "a" range.  It shows
>> the RESULT of a calculation WITHIN A RANGE (Dmax), divided by the noise
>> (Dmin), but the result is NOT "a" range.
>
> Austin,
>
> First off (Dmin) I was hoping to see how you'd respond to Julian's point
> that MDS is not always defined by noise. Your eq is based upon noise, but
> all definitions reference min disc signal. Where are you when the min disc
> signal is not defined by noise?
>
>> A VERY simplified example that I've used time and time again while
>> contradicting what you have been saying, but you seem to fail to grasp:
>
>> A RANGE of 0-5V (which could be stated as a range of 5V) with 1V noise
>> has a dynamic range of (5-0)/1 or 5.
>>
>> A RANGE of 0-5V with 1/2V noise has a dynamic range of (5-0)/1/2 or 10.
>>
>> Note, the RANGE is identical, but the DYNAMIC RANGE is not.
>
> I don't get how you can have a range of 5-0 when noise is 1. How do you get
> a range below noise? Doesn't noise limit your range on the low end, ie
> define your MDS, just as saturation/clipping does on the high end?
>
> Seems to me in your examples above you'd have two choices for each scenario:
>
>> A RANGE of 0-5V (which could be stated as a range of 5V) with 1V noise
>
> This could be ISO = DR = Dmax - Dmin.... = 5 - 1 = 4, which I *think* is how
> Julian would approach it.
>
> or Austin = DR = range/noise.... = (5 - 1)/1 = 4 which would appear to
> account for noise twice, though when noise is assigned a value of 1 it
> doesn't affect the final DR value (while conceptually it's way different).
>
>> A RANGE of 0-5V with 1/2V noise
>
> This could be ISO DR = Dmax - Dmin.... = 5 - .5 = 4.5
>
> or, Austin DR =(5 - .5)/.5 = 9
>
> Obviously, I must be mistaken about my assumption of noise and MDS...
>
> But the greater surprise is your definition of Dmax as a range. For your
> interpretation to make sense, your Dmax would need to be the entirety of
> what Julian considers to be dynamic range. For instance, if you were
> determining the the DR of a frame of film, isn't Dmax just the max density
> of the film? By your definition Dmax would be the entire density range of
> the film?
>
> So is DR effectively = density range / noise?
>
> If it were that it would be pretty easy to say so. Never seen it in any of
> the sources cited.
>
> The problem is that where sources are cited as definitions, those same
> sources don't also show numbers applied in the formula, so we can't see
> who's approach they support.
>
> Todd
>
> ------------------------------------------------------------------------------
> ----------
> Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe
> filmscanners'
> or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or
> body

----------------------------------------------------------------------------------------
Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe 
filmscanners'
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or 
body