[filmscanners] Re: Dynamic range

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

Hi Austin

> What, specifically, do you believe that write-up disagree with me on?

Is it that you did not read my post, did not get my point, or just disagree?

> Their equation for dynamic range is precisely what I've used...

I think I should just requote myself until I understand what you don't get
from me. Okay, I may embellish it a bit.... I'm saying:

Note, there are at least two critical differences between The Higgins
diagram with Austin's terms, and the Analog Devices white paper figure 5.

1). What Higgins calls "Largest", Austin defines as, "the maximum signal
level minus the minimum signal level, and is the largest range or absolute
range that the signal can go from <=> to"...

This RANGE is what Austin uses as the numerator in his DyR equation...

However, In figure 5 this RANGE is called: Dynamic RANGE - The difference
between the loudest and quietest representable signal level, or if noise is
present, the difference between the loudest (maximum level) signal to the
noise floor.

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)

The key is not that one is expressed as a difference, the key is that what
Austin uses for his numerator (or Dmin) is the range between maximum signal
level and minimum signal level, whereas the Analog Devices paper just uses:
loudest (maximum level) signal.

Austin takes the range between max signal and noise, what they consider to
be the DyR, and makes it the numerator of his ratio, with noise as the
denominator.

This gets to the issue of whether DyR defines a range or a resolution. I'm
contending that the Analog devices paper shows it to the a RANGE, the
useable range of the device, the range between noise and clipping. Not the
range between noise and clipping relative to noise.

2). Further, Austin has claimed that if Higgins had meant for the numerator
to simply be what Austin calls "maximum signal level" he would not have
illustrated the concept of "Largest" with a double sided arrow which spans
the range between noise and clipping (what fig 5 calls DyR).

However, in figure 5 we clearly see them point specifically to the highest
signal (Peak Level) as a single point where anything greater would be in the
"distortion region". In fact they define it as the clipping point. This is
the value they use as their numerator.

Remember, their definition of DyR is:
Dynamic Range = (Peak Level) - (Noise Floor)

Austin-s definition is:
((maximum signal level - minimum signal level) - noise)

The difference again is that Austin claims DyR to be (essentially) the
useable range of the device (between clipping and noise) relative to noise,
while Analog Devices claims it to be the the useable range of the device:
the range between clipping and noise.

Now I understand that I'm suggesting that Austin's minimum signal level will
be noise, and I do that because I'm assuming in any relatively well designed
piece of electronics that would be the case, and I believe that is what this
paper is written to.

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.

That is my reading of it anyway, and right or wrong, that is my point.

Todd

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