Camera Exposure and Metering Modes
Many DSLR owners have never ventured beyond using basic point and shoot functionality on their cameras. Even for those who DO venture beyond “P” on their cameras selection dial, camera exposure and metering modes are often overlooked, and there’s absolutely no problem with that if you’re happy with the results your getting. But most of us start to realise pretty quickly that simply placing the camera into manual mode, adjusting aperture and shutter according to the meter reading in our viewfinder isn’t enough to get correctly exposed photos. Why not?
The reason is that our DSLR’s have a number of different methods for measuring light, and they’re not all suitable for every situation. In fact, quite the opposite is true. Often a specific scene is best assessed with only one of the available metering modes. In order to select the best metering method for any given scene, we need to understand how the measurements are taken and processed.
For the most part, there are 4 common types of metering modes available on modern SLR cameras. Lets talk about what they are and situations where the different modes might be useful.
Centre-weighted metering can be found on just about any SLR or DSLR. It’s probably the oldest style of metering, and also the most inaccurate. Centre weighted metering measures the levels of brightness in the centre of the frame, works out the average brightness across that area, and then applies the value to the entire frame. Centre-weighted metering is not very good for scenes where the levels of brightness vary across the frame.
In contrast (no pun intended) to centre metering, spot metering can provide excellent results in scenes that have varying levels of contrast. This mode measures a very small area from the centre of the frame and applies that absolute value across the frame. Use this mode with AE Lock (Exposure Lock), but beware that it takes some experience to know exactly where to take the measurement from. The basics of use are this: Set your camera to spot-metering mode, then point the absolute centre of your frame at the area where you want to take the measurement from. Press your “AE Lock” button. That’s the measurement done, now recompose your frame and take the shot.
This mode is only found on Canon EOS cameras. Partial metering is similar to spot metering, and usage is the same, but the difference here is that the area used to take the measurement is somewhat larger. Rather than a measurement circle of 4% or 5% used in spot mode, partial uses an area that is closer to 10% of the total frame.
This is the default metering mode for most SLRs and there’s a very good reason for this. Matrix metering is quite complex, and also quite intelligent and will, in most cases, take the most accurate readings. Matrix mode takes multiple readings across the entire frame (hence the term matrix) and then suggests a reading based on the average of all points of measurement.
So where would we use these different modes? I would always recommend experimentation is the best teacher, but I will give you a little guidance here based on my own opinion. Use spot or partial modes especially for high contrasting environments such as a rock concert. The dark background can confuse the other types of metering. Take your measurement by pointing the camera at a performer before taking your shots. You can try matrix mode out for just about everything else, keeping in mind that the cameras in-built metering should be used as a rough guide only. Always use your best judgement to override a suggested exposure setting if your gut tells you so and as I mentioned before, don’t be afraid to experiment - particularly if you’re using a DSLR as you have nothing to lose.