Re: [AMIA-L] Question regarding film resolutions

[Richard Wright-ARCHIVES <richard.wright@xxxxxxxxx>]

John and all: regarding film grain and digitisation, I have the
following calculations:

Size of a grain: I've found this hard to pin down, and of course it
varies with
film type.  But grain size is 'a few microns':
"Although individual grains are only a few microns across ..." 
Berry & Burnell "The Handbook of Astronomical Image Processing" 


If you then use 10 microns as the grain size, you get:
10 microns => 100 'grains' per mm
Academy 35: 2200 x 1600 'grains'
16mm: 1000 x 750 'grains'

Of course, if you say the grain is 5 microns, you have to double those
numbers.

If you follow the EBU film digitisation guidelines:
(EBU Technical Document 3289:  Preservation and Reuse of Film Material
for Television;
Suppl 1: guidance for broadcasters)
 you get lots and lots of information, but allowing for grain and camera
lens gives:
"In a typical 35 mm camera the lens reduces the resolution to 130 pixels
per mm"
(Sect 4.1.2.1)

So using 130 pixels per mm on standard apertures gives:

35mm: 2860 x 2080 pixels
16mm: 1300 x 975  pixels = lower than (some) HDTV standards

If you want the detail, the EBU reference is here:
http://www.ebu.ch/CMSimages/en/tec_text_r101-1999_tcm6-4699.pdf 


Regards, Richard
>Richard Wright
>Technology Manager, Projects
>BBC Information & Archives

http://www.bbc.co.uk/

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