Digital BW, The Print

> I don't know if you are listening to me any more but I'll try.
> Here's a light hearted attempt.  Maybe it'll be amusing enough
> to bother reading and ease the tension.

Roy,

I do read all your posts!  I just don't have the time right now to devote to
responding.  I believe I've simply stated my case, and it should stand on
it's own.  I do want to write this up, as I feel it is important enough to
devote the time to it when I have the time.  I have discussed this very
topic with others (far smarter than I am, and also professionals in the
field), and they, too, view life the same way...so it appears the only thing
I'm doing is attempting to change your mind, and it appears you don't want
to change it.

<snip>

> This is approximately what you've been feeling in some of the
> posts.  Close maybe?

Sure.

> Roy:  Well I've a couple of rulers that're different. Can
>       I tell you about them?
> Austin: (you'll have to supply this one!)

OK ;-)  But they're only different if you look at them sideways/with your
eyes closed/underwater and hold the ruler above water/drink a lot of
gin...etc..

<snip>

> Roy: Hey, I have another that also goes from 1 to 16,
>     but it only has 4 steps.
>
> Austin:  Jees, Why don't you just go buy some decent rulers.

GLASSES, I'd say buy some decent GLASSES ;-)

<snip>

> Austin:  This is getting nuttier and nuttier.

Sounds like I was right about the gin ;-)

<snip>

> Roy:  Well its really starting to look good now.  In fact
>       it turns out that there really are numbers on all
>       the marks.  But, they sure don't look like we
>       expected.  Here's what's written on the marks:
>
>       1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32.

Ah, but that has to do with the area of a circle...vs radius...  You could
very well re-mark those anything you want...like relative area, then it
would be marked 1, 2, 4 etc. (as a divisor), or 1, 1/2, 1/4 etc.

Area = pi * r**2

For a 50mm lense, f1 has an opening of 50mm...and the area (which is
directly proportional to the amount of light let in) is 1963 sq mm.  f1.4,
which is 1/2 the amount of light is 1001 sq mm, f2.0 is 490 etc.

> Well obviously the rulers are on my lens,  The first one
> is the aperture ring and the second one is the shutter
> speed.  I wanted to illustate how different an exponential
> series is from a linear series.

But they aren't different...they ARE both linear.  One is merely part of an
equation that represents the actual area of the opening...it's merely a
representative number and could have been the actual area for that matter!

<snip>

> Going back to my two "rulers", we know that the aperture
> scale is a series of equivalent intervals.  They don't
> really "look" equivalent but they sure work that way.

But to me they do look that way, as I understand what, exactly, they mean.
Any way, you are talking about representative numbers on a scale.

> Similarly, the intervals of the shutter speed series are
> all equivalent. In going from 1 to 16 there are 8 intervals
> on the aperture scale

What numbers happen to be marked on the scale is not relevant.  There are,
theoretically, an infinite number of intervals IN the aperture scale
(typically not in the shutter scale though)...the numbers are merely a
marking of a point along the scale.  Scale markings have nothing to do with
dynamic range, unless the interval between markings is the smallest
discernable signal, and in the case of the aperture, they are not.  In the
case of the shutter speed, they typically are, BTW, as there are typically
not intermediate shutter speeds.

<snip>

> In going from 1 to 16 there are 8 intervals
> on the aperture scale but only 4 intervals on the shutter
> scale.

<snip>

> For the same overall
> ratio of (16/1) we come up with two different numbers of
> steps even when we've used the same "photographic" sense
> of one step = one stop.  Actually could also have tick
> marks on the lens for fractional stops, giving more
> possible "number of steps" values.

This is a misunderstanding.  You are assigning 1 as the minimum discernable
"signal", and it is not.  You are not comparing two dynamic ranges here at
all.

It was a nice try, but your example here is erroneous.  I'll read the rest
of it later, but I believe this misunderstanding really shows why you are
having trouble understanding what really dynamic range is.

As a note, the dynamic range of the aperture is FAR larger than that of the
shutter speed, since shutter speeds have fixed intervals, and apertures do
not.  And yes, there IS noise in the aperture system (as well as the shutter
speed system, but the shutter systems noise should be far less than the
minimum discernable change between shutter steps), as it will only hold so
much of a tolerance...and as I've said before, mechanical systems do have
dynamic ranges.

Regards,

Austin