My Canon 350D camera has three metering modes – evaluative, partial and centre weighted average.
I preset my camera to evaluative for most of my shots as it gives good all-round metering from the 35 ‘zones’ it creates on the image.
However, the other main metering mode - ‘centre weighted average’ attempts to optimise the meter for the middle point of the frame, and is useful for when taking photos of say a shaded object in a bright scene so as not over-expose this object. The ‘partial’ setting is a combination of the two which gives greater influence to the centre point, but also takes account of the whole frame (but to a lesser extent).
The camera’s meter is easily confused however, as it ‘expects’ pictures to be made up of averagely brightness. Thus, if you are not careful, dark scenes are over-exposed, and bright scenes are under-exposed.
The same can happen with printing images if the printing process automatically compensates for the brightness of the scene. I was very disappointed with a poster sized print i had made of an image of a man painting a wall white which when printed was a dirty grey !
Here is an example of a dark image i took whilst on a walk. it’s of some tires on a black tarpaulin on the edge of a farmer’s field
This was the first image, metered using evaluative metering from the camera
I then adjusted the exposure compensation to +1EV which clearly made the effect worse !
i then gave a negative exposure compensation of 1 stop (-1EV)
This still seemed rather bright on my LCD screen so i dropped it 2 stops (-2EV)
This looked too underexposed on my camera LCD screen so i backed it off to –1.3 EV.
On a proper calibrated computer monitor i prefer the –2EV adjustment which shows how wrong the automatic meter can be !
The following pictures were both taken using the camera’s automatic setting (with a minus 1 2/3 EV exposure bias to avoid blowing out the highlights in the covered statue)
This first one was taken with ‘average’ metering.You can see the background foliage is slightly lighter
the second shot is slightly darker and uses pattern metering which spot meters across the image (including the quite statue)
This was a demonstration shot to show the effect of different sorts of metering (the composition of the shot is quite uninteresting!), but it’s useful to zoom in on the statue to see the difference between the two types of metering for this subject. As you can see, the pattern metering works better as it takes account of the particular brightness of the statue when metering the whole picture
