Overriding the meter

Evaluative metering and exposure compensation

All current Canon DSLRS, apart from the 1300D, include four metering modes: Evaluative, Centre-weighted average, Partial and Spot. The most sophisticated of these is Evaluative. It divides the viewfinder into a number of zones – from 63 zones in the EOS 1300D to 216 zones in the EOS-1D X Mark II – and then compares the individual readings from each zone before calculating the exposure.

Unlike the other metering modes, the subject of the photo doesn’t need to be slap-bang in the centre of the frame as the camera uses the active autofocus points to determine where the subject is – it presumes that it’s under the AF point that’s achieved focus – and it prioritizes the exposure accordingly.

As good as it is, there are times when Evaluative needs a helping hand, in the form of exposure compensation, which you can apply in any of the Creative Zone modes – including Manual mode with Auto ISO enabled on some cameras. On high-end Canon DSLRS you dial in compensation by turning the large Quick Control dial on the back of the camera – to the right to make things brighter, or to the left to make the image darker. The majority of entry-level Canons require you to press the Av +/- button and then rotate the Main dial on the top of the camera, next to the shutter release, instead.

Here’s the thing: before coming up with an exposure, Evaluative metering has already effectively applied its own compensation, taking into account the brightness, colour and focus information. The other three metering modes don’t do this, so you’re likely to need more substantial adjustments when you set exposure compensation in theses modes.

Dialling in some positive exposure compensation corrects this for the subsequent shot the whole evaluative meters exposure scene, but biases af point towards the active

I’ve focused on the london eye here, but the camera wants to make the bright sky a mid-grey tone