How many megapixels do you get from film?

Well that’s a question. There’s no easy answer, but I’ll discuss it a little here. If you just want the figures, scroll down to the table!

The number of film “pixels” (grains) does not equal to the resolution of the film – unlike pixels on a digital sensor. For now let’s ignore this fact and get down to some numbers.

I’ve checked in various places, and the consensus seems to be that a frame of 35mm film (24mm × 36mm in size) has up to 20 megapixels, assuming the film is fine-grained, and was exposed and developed properly. We arrive at this number by scanning a negative at progressively higher resolution (in terms of dots per inch, dpi), seeing smaller and smaller artefacts in the picture, until we reach a stage where increasing the dpi of the scan does not yield more smaller grains in the scan. At this stage, we see what digital resolution we have scanned the image at.

There’s massive scope for mishandling film and reducing the fineness of the grains, which means we will effectively lower the digital resolution of the negative. It’s extremely hard to judge this here, so we will assume that our hypothetical photographer was careful in handling his film. We will also ignore any loss of sharpness caused by imperfections in the lens.

Taking the optimum value of 20 megapixels for a 35mm frame, and extrapolating this to other film formats…

Format Size (mm) Megapixels
35mm (135) 24 × 36 20
120 6×4.5 medium format 60 × 45 63
120 6×9 medium format 60 × 90 125
5×4″ large format 127 × 102 300
10×8″ large format 254 × 203 1,200

As I touched on earlier, raw “pixel” (grain) count doesn’t necessarily give better resolution with film. Grains on film are different sizes and not in a neat grid, like pixels in a digital camera’s sensor. True resolution, as seen with the eye, has more to do with resolving closely-spaced pairs of fine lines.

Given that you usually need more film grains than digital pixels to achieve the same optical resolution as seen by the eye, it’s a reasonable assumption that my 35mm SLR (~20 megapixels) is similarly performing to my Canon 450D DSLR (12 megapixels).

Some high-end digital cameras such as the Hasselblad H4D-60 can now achieve 60 megapixels but this still doesn’t come close to professional medium format cameras using 120 film (still used for lots of magazine and glamour photos), or large-format cameras (still almost exclusively used for landscape photography).

So there you have it. Film can produce a considerably higher optical resolution than digital cameras, when used carefully.

5 Comments

  1. Stu
    February 13, 2011
    Reply

    Plus, it handles the extreme of clipping more gracefully. And you will always be able to decode the RAW file format 🙂

  2. Jonathan
    February 13, 2011
    Reply

    You’re not wrong, Stu. I love film, it’s such a fun medium to work with.

  3. Paul
    January 4, 2012
    Reply

    Film – I remember that – the smelly chemicals and working in total darkness.
    Film is a precise medium. Exposure and focus are narrowly defined, especially exposure. Just the ticket for the obsessive-compulsive!
    Another thing that I don’t mind leaving behind is the retouching light box with its supply of pencils, magnifiers, and long hours.
    Digital photography is liberating, enabling medium. I really like digital photography.

    • Jonathan
      January 4, 2012
      Reply

      Heh, I guess the fact that I’m borderline obsessive-compulsive makes it the ideal medium, then!

      I’m young enough that my only past use of film was single-use cameras on holiday as a child. Since I got into photography as a hobby, I started off with digital but soon became fascinated with the black & white process. In fact, just this evening I purchased some larger trays so I can make 16×12″ prints in my darkroom 🙂

      Happy shooting!

      • May 12, 2014
        Reply

        Paul: It’s the opposite for me…..I feel that going back to film from digital is liberating, as I am now in control of the exposure rather than the computer of the camera. My skills have improved tremendously in the past year, and I am to a point where I can be out for several hours and only take a dozen “good” photos. In contrast my brother went to a concert and took 3,000 photos of the band with his 5D Mark ii and is struggling with going through all of them to find some that he likes and are focused (dim lighting is tough!). To each of us our won though, right?! 🙂

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