Digital BW, The Print

I have problems with this response. Maybe it's just a lack of 
understanding on my part, so please enlighten me. Questions in-line below.
--
Bruce Watson


CDTobie@... wrote:

>
> In a message dated 4/28/06 5:28:30 PM, a_pettit_jr@... writes:
>
>
> > The question IS : I have a 6x7 film camera. If I purchase a refurb'd
> > scanner I can create 142 Mpix files.... Is this really 24 times better
> > than a 6 Mpix digital camera ?
> >
> > Whats the generally accepted rule to equate analog (film) scans to full
> > digital camera images ?
> >
> There is no rule, as there is more or less usable data in a given digital
> photo or film scan, depending on the content, lenses, ISO, filmstock 
> and many
> other factors. But in general, a digital photo has more meaningful 
> data per pixel
> than a scan. 

How can this be? My understanding of a pixel, any pixel, from any 
digital camera or film scanner, is that it's generally a square and can 
have exactly one RGB value, at some number of bits between 8 and 16 
(depending on the ADC), usually padded out to fill the 16 bit data words 
used by computers. That is, it can have at most 16 bits of R, 16 bits of 
G, and 16 bits of B. If you reduce to grayscale, you get at most 16 bits 
of luminance value only.

Besides the size of the square and the RGB value what "more meaningful 
data" are you talking about?

> High rez scans from small film are all about one level or
> another of grain definition... and while there can be ISO noise in a 
> high rez
> digital photo, there is significantly more info per pixel, especially 
> when shot with
> high end cameras, high end lenses, and some user expertise.

My understanding is that it's impossible to actually image film grain 
(that is, grain clumps or the resulting dye clouds in color films) with 
a scanner. The grains when seen under a microscope are generally 
fractals. The fractal detail (actual shapes) is considerably smaller 
than the 3 micron size of the best aperture on the best drum scanners. A 
3 micron square is at best a poor representation of most film grain.

 From a film scanner then you get what I call "digital grain" which is 
not at all the same as film grain. It's a different kind of information, 
largely due to making a deterministic sampling of a stochastic media. 
Very similar to what a digital camera does - making a deterministic 
sampling of the stochastic scene being transmitted to the sensor by the 
lens.

So again I'm curious as to what this "significantly more info per pixel" 
is. I don't understand it, please help me see what you are talking about.

>
> If you shoot large enough film you have more data because of the 
> larger film
> size in relation to grain size... so that 4x5 and 8x10 scans can be 
> done at
> levels that don't have much to do with film grain (unless you are 
> blowing them
> up to huge sizes). Here you can capture more data that a 16.7 
> megapixel SLR
> image. Exactly where the changeover occurs (of more data in scanned 
> film versus
> more in digital capture) is an open question. Studio backs move the 
> tradeoff
> point even higher, but you apparently are not making that comparison, 
> though it
> might be the more obvious one...
>
> The general statement is that digal SLRs have outstripped 35mm, and 
> are very
> competitive with medium format, for actual detail resolution; but the 
> issue
> can be argued endlessly, based on a wide array of factors.
>
> C. David Tobie
> Product Technology Manager
> ColorVision Business Division
> DataColor Inc.
> CDTobie@...
> www.colorvision.com