Size matters (2)

As I said earlier, in sensors, bigger sizes are better.  Let me expand on that a little.

A bigger sensor means five essential things:

  1. Lower “noise” (and hence, greater ability to shoot in low light).
  2. Greater ability to use selective focus (“blur the background”).
  3. Better use of the maximum resolving power of the lenses’ glass.
  4. On an SLR, a bigger, brighter viewfinder.
  5. Greater ability to use small apertures (high F-numbers”), which otherwise lead to distortion due to the bandwidth of light – so this is physics, and will not be overcome. This is why lenses have a “sharpness sweet spot” – say, at around f/8 on a full-frame camera with a typical lens.

And less fundamentally, but very importantly in practical terms, for those of you choosing between full-frame and crop sensor SLRs, a larger sensor also means that the same wide angle lenses are wider on the full-frame camera.

So what sensor sizes are there?

  • A typical point-and-shoot: 6 x 4 mm
  • Four Thirds (as used in Four Thirds and Micro Four Thirds cameras): 18 x 13.5 mm
  • APS-C, the sensor used on a typical crop SLR, like a Canon 60D or a Nikon D90: around 22 x 15 mm
  • APS-H, a Canon format, as in my 1D Mark IV:  28.7 x 19.1 mm
  • And “full frame”, as in a negative: 36 x 24mm

And every step smaller means less ability to close down the aperture and stay sharp, less ability to blur the background, and more noise.

The benefits of small sensors are the small size, weight and cost; the ability to use small and hence cheap lenses; the fact that they make lenses appear longer (which is good if you are a sports shooter, but bad if you are a wide-angle shooter); and the ability to get close, so point-and-shoots are usually very good macro cameras.

Leave a Reply

Your email address will not be published. Required fields are marked *