Re: A Plea For Film Digitization (was: Digital restoration of silent films)

From: David P. Hayes
Newsgroups: alt.movies.silent
Date: Friday, January 16, 1998 10:07 PM

In my last post on this subject, I quoted Jon Mirsalis (

>The point is that I can tell you that film emulsions, at the microscopic
>level, are incredibly irregular. A typical silver halide crystal is oddly shaped
>(not at all round…more like a splop of paint) and varies in size from about
>0.5-5 microns depending on the temperature you developed it at. This fits with
>David's assertion that computer digitization may actually be using higher
>resolution than it needs to. I posted the mathematical analysis on the
>amount of storage space needed per frame a few weeks back and am too lazy to
>reproduce it now, but I think it was around 15-20 MB per frame, but the point is that
>you could probably store the information to a resolution indistinguisable by the
>human eye with 20% of that.

The passage Jon cites is from his posting: Re: Digital restoration of silent films (was Re Chaplin & DVD) 12/24/1997 Message-ID: <>

The pertinent passage reads:
>>>So, if you want to digitize a 35mm film with NO loss of resolution, you'd
>have to use a resolution of 5333X4000 pixels for each frame… .25.4MB per FRAME

>Here I think you might be a bit too low. The diameter of a silver grain is
>about 2-micron, and that is the resolution-limiting factor of film. Therefore,
>a 35mm frame with a usable picture area of around 19 mm x 24 mm
>contains approximately 9,500 x 12,000 grains = 114 M grains (i.e., MB)
>per frame. In practice, the human eye can't distinguish grain-to-grain
>differences, so you could probably reduce this number by a factor of 5
>without being able to detect it with the human eye, and this would bring
>it to about the number you calculated.

David Hayes


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