re:Digital vs Analog (might be backwards!)

[P3D Michael Kersenbrock <michaelk@xxxxxxxxxxx>]

> This can't be right (about film, I mean).  In order for film to behave
> as you say (with light-darkened silver halide crystals acting like a
> halftone), then adjacent crystals would have to have knowledge of what
> their neighbor is doing (i.e., "this area is supposed to be 50% grey,
> and my neighbor is on, so I should be off").  In the digital halftoning
> world, this knowledge is present in the computer program which is
> approximating a true grayscale value by turning on and off a certain
> ratio of pixels in a given area.

Why?  Does an acorn have to understand cell division to grow a leaf?  If
it acts like it's halftoning, then it is, whether it knows it or not.
The CCD cell in a digital camera is an "analog" device, so why isn't
that digital camera called "analog"? 


> >This view of the film also explains and makes reasonable data I've seen
> >in recent news stories talking about digital images that claim that the
> >equivalent resolution of 35mm film is 3 million pixels, not the much larger
> >numbers put forth in this forum.
> 
> Like digital imaging companies don't have a vested interest in convincing
> a skeptical photographic community that film resolution really isn't as high
> as it is?  A reasonable estimate of the resolving power of film is 100 line
> pairs per millimeter.  These numbers come from the film companies themselves.
> By simple math, this is 200 lines/mm, giving a 33mmx23mm 35mm film chip
> the equivalent of about 6600x4600 pixels, which is a little over 30
> million pixels.  I'm sure they'd love you to believe it's only a tenth
> of that.

You are not addressing that of which I wrote.  Each pixels in a common
digital image contains 24-bits of information.  I don't see that to 
be true in the film's case in the way measured.

With digital, each pixel can be completely stark-black or completely 100% white
at full resolution .... or some exact value inbetween.  I don't believe that is 
true for each line in your resolution test as it is usually measured (correct
me if I'm wrong on that).

Consider the situation where a picture is taken and the background is
*COMPLETELY* white.   If *one* pixel-width circle of the image is only 
*slightly* darker... say 1% darker.  Will that film faithfully resolve
that one pixel with the correct 99%-brighness value?  The digital camera
could.  And even more-bits-per-pixel are available now in scanners so
the one-pixel dot could be even less different.

I can't see that the comparison of pixels is one-for-one.  I'd guess that
each digital bit  is "worth" perhaps eight film-bits, so using your numbers, 
35mm film is  equivalent to about 4 million 24-bit pixels.  That's
just a SWAG, but I think it's less than the full 30 million.

Or so it seems.   Correct my logic error (or terminology error
which is often if not usually the case)  if there is one!

Mike K.


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