[filmscanners] Re: Dynamic range

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

To David and Austin

Austin replies to me:
>> Let me repeat, this paper says DyR is: if noise is present, the difference
>> between the loudest (maximum level) signal to the noise floor.
>>
>> This is in contrast to Austin who says DyR is: (maximum signal level -
>> minimum signal level) / noise)
>
> They are exactly the same equations, as I've shown countless times...one is
> in log and one is non-log.  Subtraction using log numbers is EXACTLY the
> same as division using non-log numbers.

Look, I'm not mathematically minded, and I do sometimes confuse what types
of values are expressed in log form and which aren't. So I can't always be
trusted to use the DyR equation in it's proper form, i.e., max - min vs
max/min. But look at those slips as typos and don't assume it means I don't
appreciate that when used properly both mean the same thing. I am confused
in usage and execution, not concept.

>> So, in summary, I believe this paper shows that dynamic range is a range,
>> the range between the noise floor and clipping - which is in opposition to
>> Austin's premise that DyR is a resolution.
>
> Come on, Todd, the paper CLEARLY says dynamic range is a resolution.  Why on
> earth do they say so many times that you need so many bits to represent a
> particular dynamic range?  Forget the diagrams, you are confused by them, as
> they clearly represent two different things.

I think Roy and Julian have answered this better than I could. I would just
say that to really get at this I think it needs to be looked at from an
analog perspective, so we do not let the relationship which exists between
bits and DyR in the digital world confuse us as to what DyR IS. The bits are
merely carriers of DyR, they are not what DyR is. I know you and David know
this, but you say thinks like above which confuse the issue.

Here's another obscure example to demonstrate my point that will make the
purists puke... but lets just try it. Say we have a vessel of freshly
squeezed milk. Let's pretend there are some curds or solids in the milk
which have settled to the bottom. Let's call them noise. And there is some
creme which has risen to the top. Lets call that saturation or clipping. I'm
going to say the aspect of the milk I am interested in is the skim milk
between. That volume of milk is my Dynamic Volume. For every similar vessel
I have of fresh squeezed milk, the quantity of Dynamic Milk within that
vessel may be different, depending on the relative amounts of noise and
clipping that accompanies it.

So, lets say I have one particular 250 oz vessel which has 1 oz of noise
(solids) and 49 oz of clipping (creme). That leaves me with 200 oz of
Dynamic Volume in that Vessel.

Whether you want to express that volume as a difference or a ratio doesn't
really interest me.

Now if I have 20 calves that each need to be bottle fed 10 oz of milk, I
know I need 20 10oz bottles to carry my Dynamic Volume of milk. However, the
Dynamic Volume from that vessel has not now become 20 bottles, it is still
200oz.

Okay, enough of my nonsense.

Todd


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