This is a section that can easily confuse some people but to be honest it is very simple in its understanding and execution. At the end of the day, whatever you are shooting, there is just one correct exposure (unless you are purposely under or overexposing for effect), but there are many different ways of achieving that exposure using the cameras metering modes and that is what confuses people.
We cover metering in more detail in the next module but let’s cover the basics.
There are 4 or 5 metering modes in most DSLR’s and the main ones are:
This is what most people would use. Your camera takes light readings from across the entire viewfinder and uses an average to give you a reading. This is great for most, general photography and will usually give you great results.
However, there are times when this method will throw out poor results leaving the photographer thinking they did something wrong.
If for example, there is a particularly bright area within the frame or shot (such as the sun in a sunset) the camera will “blink” at the brightness and do a digital squint…i.e. it will either close the aperture or speed up the shutter to prevent too much light getting in and overexposing the image.
Of course, this will then make the rest of the image darker. To combat this we could use the next mode of metering…
This mode will only take a light reading from the centre portion (about 30%) of the viewfinder. So, if you were to have the sun ANYWHERE other than the centre of the frame, the meter reading would not take the bright sun into account as much as it would using evaluative…it ignores the brightness to an extent.
This should produce a slightly more realistic image with the sun slightly overexposed but the rest of the image well exposed.
This mode of metering is great for shooting subjects that are heavily backlit. Using evaluative metering, the camera would expose for the whole scene and again squint at the brightness behind and underexposing the image. The subject would then be a silhouette (great effect if that is what you are after).
By using the centre-weighted method, the camera will expose for the central area so place your subject there and you should get a well exposed subject but over exposed behind (oo err missus)!
This is similar to centre-weighted but more extreme. The camera will expose for only a tiny (3-5%) of the image. You can decide which part to expose for but most people use the centre of the screen/viewfinder. You can aim this like laser targeting to expose for whatever part of the scene you desire.
For example, if a portion of the image you are shooting is particularly dark and shaded but you really need that to be well exposed, you would aim the centre spot at that, press the shutter lightly to get a reading and then shoot.
Like I said, we will cover this in more detail in the next module but that is metering in a nutshell.
Now, an important thing to remember after watching that short video is that when the exposures change, so do your camera settings. For the example in the video above, I was set to Shutter Priority so I knew the shutter speed would not change…only the aperture (which opened to let more light in for the second shot).
If I was in Aperture Priority mode, the change in exposure would have to come from the shutter speed meaning the speed could slow significantly (to allow more light in from the shaded area) which could lead to camera shake and a blurred image.
Be aware of this when changing your metering settings…