exposure - What situations are best suited for spot metering?

I have found myself using spot metering on several occasions in order to get the right exposure, such as sunsets and on bright days with a subject in the shade. What other situations are well suited for spot metering instead of the standard matrix mode?

Answer

With spot metering, the camera will only measure a very small area of the scene (between 1-5% of the viewfinder area).

Metering Mode

This means you could get a light reading for a very specific area in the frame as opposed to a general measurement for the overall picture. Using this built in meter you can tell specifically how your subject will be exposed with your current camera settings and whether you need to adjust them to get the exposure you're looking for. Using the spot meter, you're telling the meter that the subject you're pointing at is at an 18% gray level in the Zone System. If the subject is indeed in the mid tonal range, you would leave your exposure as is but if it's brighter or darker, you would have to adjust your exposure accordingly. More on 18% gray and the Zone System here.

Situations this is useful for:
- Photographing the moon
- Photographing someone indoors in front of a window
- Sunset behind the subject
- Subjects who are lit like the rest of the scene, but appear darker/lighter due to their colour. ie Black horse in a bright field
- Anytime there is a high Subject Brightness Range

How to use Spot Metering
Shooting Manually

Simply point the Spot, the dead centre of the frame on most cameras, to the area you want to meter and adjust your shutter speed, aperture, ISO etc. as needed to get the scale in your viewfinder to 0. (Or the exposure you're looking for.)

Shooting in P
Point at the area you want properly exposed, lock the exposure and from there compose your shot as necessary.

Using Spot Metering is generally more time consuming and takes a little more practice to use effectively but if you're trying to get a certain look for your photograph it usually yields better results.

See How Spot Metering Affects Your Settings
A good experiment to really see the affects of Spot Metering is to put you camera in semi automatic shooting, P, select spot metering and frame a picture of a light bulb lighting up a dark room. Point directly at the bulb and notice the settings your camera changes to try and get the correct exposure. As your move around, you'll notice even slight movements can drastically effect the settings because the metering is so specific. Try the same experiment in average mode and you'll notice you can move your camera to almost any point in the frame and get only 1/2 stop changes in shutter speed and/or aperture.