When travelling with other photographers it is common to hear someone shout out, “plus one,” “minus two” or other advice for exposure compensation. These photographers have all been advised to use aperture priority or shutter priority and to trust the cameras evaluative metering system with minor adjustments for the overall tone of the background. It’s a system that works if you want to produce average, mostly well exposed pictures of the scene before you. But of course almost anyone using a modern DSLR or even a decent camera phone can produce average, mostly well exposed[TL1] pictures of the scene in front of them. What the cameras built in evaluative metering system is not designed to do is think artistically and produce an exceptional rendition of the scene. Let me show you a simple example from a recent shoot in the Arctic above Norway.
The first picture below was taken from a moving zodiac using evaluative metering and adjusting ‘minus two’ to prevent the highlights being blown out. F8 1/2000 ISO 800. Minus two is the most you can dial in on most consumer DSLRs.
The second picture was taken 3 minutes later in manual mode using central spot metering and adjusting to make the beams of light reflecting off the water two stops above neutral (18% gray = the center of the metering scale in the view finder) F11 1/8000 ISO 800This is three stops less exposure than the first picture and you would have had to dial minus 5 (which can’t be done) if you were shooting in either aperture priority or shutter priority mode with evaluative metering.
As a photographer you can recognize the importance of the beams of light breaking through the clouds and resultant drama in front of you that results of an appropriate exposure. The evaluative metering system is looking for overall average exposure and that is all you are going to get. A good photographer will dial in plus or minus one or two stops to get a better picture but that is often not enough to produce an exceptional picture. The camera is programmed to produce average acceptable pictures, anything better is up to you.