When it comes to an SLR’s TTL (through-the-lens) metering system (as opposed to using a handheld lightmeter), it is not what you have, it is what you do with it that counts. Some 35mm SLRs have several metering systems, which will cover almost any metering situation you can think of. Some have only one metering system, but this does not mean you have to be restricted by it. If you know and understand it well enough, it will serve you as well as a camera with several. The main difference between each of them is how they react to light levels in certain parts of the viewfinder.

Shutter and aperture priority modes are very simple. You use shutter priority when the shutter speed is more important than the aperture. For example, if you want to capture a fast moving object, you would set your shutter speed to 1/500 second, and the camera will automatically give set an aperture to give you the correct exposure. Aperture-priority mode is the same in reverse. If you are shooting a landscape where the depth of field is important, you may set the aperture to f/11 and the camera will then select a shutter speed to give you the correct exposure.

Center-weighted metering is the most common kind of system. It works by measuring light from all over the viewfinder, but pays extra attention to what is going on in the center of the picture area. The image is split into two parts: the center circle and the surrounding area. The system is good when your subject is in the middle of the frame, but not great for non-average scenes or compositions.

Matrix or Evaluative or Honeycomb metering (different manufacturers call it one of these names) breaks the scene into a number of parts and reads light information from each. This system is good where there are many contrasts, shadows, etc in a scene, but it is still only satisfactory. It will leave the shot of your white Cottie dog in a bath of milk underexposed and the dark suited driver of a black limo overexposed.

Spot metering is probably the most useful. This system allows you to isolate a single part of the scene to take light reading from only that part. The actual spot is usually in the center of the viewfinder and varies in size depending on your camera. If you point your spot to anything in the scene, it will tell you how much light is being reflected from it. The mistake people make is to believe the reading given by the spot is the one which will deliver the correct exposure for that object. But if you point your camera at a white object, the meter will only tell you what exposure is needed to make that object appear as a mid-tone. The same is true for a black object. The trick is to find the object in the scene in front of you that you want to reproduce as mid-tone in your final image (ie, a shadow on a flower) and spot meter for that. Take some time to learn spot metering and you’ll see what the advantages are.