RE: [Leica] Film megabytes and some curious contradictions

[Austin Franklin <austin@darkroom.com>]

> What is the amount of bytes for film. Some say you should count the 
grains,
> but that is the wrong apporoach

I completely agree with that.  I consider the amount of bytes in film to 
where I can resolve such that the grain starts to be noticed...and 
sometimes, for grainy films, which I want the grain effect, I resolve more.

> Now current film (BW or slide or color neg) has resolution figures
> around 100 lp/mm and Techpan has 200 to 300  lp/mm. Follow this: the
> negative area has 24 x 36mm. Every mm holds 200 different lines. that is 
24
> x 200 x 36 x 200 bytes = 4800 x 7200 = 34.560.000 bytes. We need three
> colours, that is 34.560.000 x 3 = 103.680.000 thus more than 100 MB for a
> colournegative or slide.

Isn't it line pairs/mm, ie one black one white?  That would mean you are 
off by a factor of 4.

> This figure is close to my original and ridiculed calculation.

Any disagreement I have with your numbers are based on my experience, since 
I sit in front of a 5080DPI scanner for many hours a day (thanks BD for all 
those negatives ;-)  I know what DPI can suitably resolve what film from 
experience...

> Now for some  steps. It is very difficult and often considered 
unnecessary
> (pace Mike Johnston) to get on film more than 40 line pairs or 80 lines. 
And
> if we be even more general, 20 lp/mm are the best. most people would 
dream
> about. Assume now 20 lp/mm or 40 lines per mm (the best you can get in 
hand
> held picture taking, generally speaking).
> Again: 24 x 40 x 36 x 40 = 960 x 1440 = 1.382.400. Three colours would be 
3
> times this number, which is 4Mb. And with 40 lp/mm we et 5.529.600 bytes
> times 3 = 16.588.800 bytes or 17 Mb, quite close to the 20 MB I quoted as
> the conventional wisdom.

If you numbers were right (and I don't believe they are) 35mm cameras are 
not very high quality, and we should all shoot MF, since we couldn't print 
anything larger than about 4 x 6 and expect a quality image.  I scan NC160 
at 4000DPI, and barely start to resolve grain...so I know from practice 
that my negatives are FAR more than 960 x 1440.  Even Tri-X at 800 is 
around 2540DPI...

If your numbers were even close, and they aren't, no one would ever use a 
drum scanner, which scans at 8000 to 10000DPI.  My Leafscan 45 scans at 
5080, and is the gold standard for service bureaus.  If 35mm film only 
resolved to 1000DPI, why would everyone waste their money on 5x the 
resolution?  That doesn't make any sense.