I mostly use evaluative metering but every so often I get a dark photo. It’s always part of a sequence. All the photos are OK, except for one photo that’s significantly under-exposed by at least 2 f/stops. So I play around with the partial or the average metering. It’s rare that I use the spot metering. I use the AF-ON button and am not co-ordinated enough to do the proper fingering of the metering, focus,… There’s only so much I can do. So I started to research the Canon 7D’s metering system.

The Canon 7D’s metering is the first time that Canon uses the “Focus Colour Luminance” metering system that measures the focus, the colour and the luminance, across the 63 metering zones. The rules are:

  1. The metering system reads all the 63 zones.
  2. The main emphasis is done on the metering zone that matches the focusing point. If there is no focus point currently selected, either because of manual focus or because of pre-focusing, then it will be the center point.
  3. The next emphasis is done on the metering zones that are immediately next to the metering zone that matches the focusing point.
  4. Then all the other metering zones.

Now the questions are:

  • In what proportion? Trade secret
  • What’s the factor of the luminance? Trade secret
  • Any other data used? Trade secret

Please note that the occasional under-exposure of the photos has significantly dropped in frequency since my upgrade to firmware 1.2.2