VCF Suggestions (film vs. digital cameras)

[Bjørn Vermo]

On Mon, 08 Aug 2005 23:47:54 +0200, Tony Duell <ard at p850ug1.demon.co.uk>  
wrote:

>>
>> Re: "I reckon that a good 35mm camera (good meaning a top-end lens and
>> fine grain film) is equivalent to 12-20 megapixels."
>>
>> My understanding from the camera companies, which I've heard more than  
>> once
>> (and going back to 2000, before any such digital cameras existed) is  
>> that
>> they consider 35mm film about the equivalent of 6 megapixels.  It's not
>
> This may well be the case for a reasonable compact camera with a zoom
> lens, and normal colour print film processed in the the local overnight
> photo shop (actually, I think 6Mpixels is better than that...). I also
> think that a top-end fixed focal length lens, fine grain film, and
> careful processing/printing will be a lot better than that.
>

An excellent lens and high-resolution B&W film may give you up to 100  
lp/mm.
The pixel depth will be 12 bits or more.

A 36mm wide negative will accomodate 3600 line pairs or 7200 pixels.
To reliably resolve that digitally without artifacts, the Nyquist theorem  
tells us we need at least 14400 pixels.
The equivalent photodetector to match high-resolution film will then be  
9600x14400, giving us 138240000 or for short 138 megapixels.
High quality colour film can resolve around 64 lp/mm. This will give us  
3072x4608. Assuming a normal lens will work as a low pass filter, we  
forget about Nyquist and end up with 14155776 as the lower limit for 35mm  
equivalent quality,

I suspect that pixel depth is the biggest problem with current detectors.  
When I scan my slides, 3x12 bits per pixel is the minimum to avoid quality  
loss. With a scanner, you can easily gain another but by doubling the  
number of passes. This does not work with a camera, the detector needs to  
have enough depth (signal/noise ratio) to begin with,

-- 
Bjørn