Mike Sanchez
March 10th, 2004, 03:23 AM
The resolution of film.....
If one treats the output from film as any other signal processing problem then the point where noise becomes objectionable relative to the signal is the resolution limit. Considering ONLY 35mm film below (larger formats give different results), I've run the experiments described below myself.
For 400 ISO film, the equiv film resolution necessary to roughly equal a digital camera signal to noise ratio is, for a normal observer of an 11x14 image, a 3-4MP digital image from a camera with a good lens (Canon for example). I choose 400 ISO because really 100 ISO is too slow to use outside of a studio or a bright sunny day on the beach.
It is easy to check this. Shoot some Caucasian skin tones in natural light with a good 35 mm SLR. Obtain a good Nikon film scanner (a cheap scanner will add noise). Begin scanning at the Nikon's highest resolution. Examine the output on screen at a blow-up equivalent to 11x14 (takes a few seconds). Note the ugly film grain noise.
Then, set the resolution of the scanner down 15% and re-scan. Repeat the above.
Repeat until you arrive at the resolution where the noise becomes small relative to the (now blurred, lower res) signal. Take the file size of the film scanner output and divide by 3. This is the digital camera equivalent necessary to match the film speed signal to noise ratio. Now take a picture with digital cameras from 2 MP, 3MP, 5MP, and 6MP. Compare the results. 3MP will, for most observers, match the signal to noise of 400 ISO film at 11x14 size. If you do trilinear or bilinear interpolation the 3.2MP cameras are often better than ISO 400 film for 35mm cameras.
For 400 ISO color film (Kodak or Fuji....but Fuji will have less noise by quite a bit) a mildly discerning person can mostly get equivalent or better results with a 3-4MP camera.
For ISO 100 speed film a 6-8MP digital camera will give the same resolution results.
Backing up modern digital images to film introduces large noise, color shifts, could result in degrdation with time, etc.
The only reason to continue to use film is the following: If there is ever a widespread lack of electricity a few pictures of your kids, in print albums, will be valuable in the extreme. Photography was invented and perfected BEFORE widespread electricity availability.
We have only had reliable electricity for about 70 years. I continue to use film for key photographs of my children that I place in albums in fireboxes.
For everything else I burn DVD's and cross my fingers that electricity will be available in my old age.
If one treats the output from film as any other signal processing problem then the point where noise becomes objectionable relative to the signal is the resolution limit. Considering ONLY 35mm film below (larger formats give different results), I've run the experiments described below myself.
For 400 ISO film, the equiv film resolution necessary to roughly equal a digital camera signal to noise ratio is, for a normal observer of an 11x14 image, a 3-4MP digital image from a camera with a good lens (Canon for example). I choose 400 ISO because really 100 ISO is too slow to use outside of a studio or a bright sunny day on the beach.
It is easy to check this. Shoot some Caucasian skin tones in natural light with a good 35 mm SLR. Obtain a good Nikon film scanner (a cheap scanner will add noise). Begin scanning at the Nikon's highest resolution. Examine the output on screen at a blow-up equivalent to 11x14 (takes a few seconds). Note the ugly film grain noise.
Then, set the resolution of the scanner down 15% and re-scan. Repeat the above.
Repeat until you arrive at the resolution where the noise becomes small relative to the (now blurred, lower res) signal. Take the file size of the film scanner output and divide by 3. This is the digital camera equivalent necessary to match the film speed signal to noise ratio. Now take a picture with digital cameras from 2 MP, 3MP, 5MP, and 6MP. Compare the results. 3MP will, for most observers, match the signal to noise of 400 ISO film at 11x14 size. If you do trilinear or bilinear interpolation the 3.2MP cameras are often better than ISO 400 film for 35mm cameras.
For 400 ISO color film (Kodak or Fuji....but Fuji will have less noise by quite a bit) a mildly discerning person can mostly get equivalent or better results with a 3-4MP camera.
For ISO 100 speed film a 6-8MP digital camera will give the same resolution results.
Backing up modern digital images to film introduces large noise, color shifts, could result in degrdation with time, etc.
The only reason to continue to use film is the following: If there is ever a widespread lack of electricity a few pictures of your kids, in print albums, will be valuable in the extreme. Photography was invented and perfected BEFORE widespread electricity availability.
We have only had reliable electricity for about 70 years. I continue to use film for key photographs of my children that I place in albums in fireboxes.
For everything else I burn DVD's and cross my fingers that electricity will be available in my old age.