Take a Light Readingby Laurie McArthur
Average light is half way between light and shadow. If it's overcast there isn't so much difference between the two extremities as when it's sunny but you still should take a reading of the average light.
Identify Average Light
If you are metering off some trees and scrub in full sun you'll probably find that the scene makes it's own shadows within the foliage. Be careful because the amount of sun and shadow can be confusing.
If metering a tree, aim your meter such that you read off half sun and half shadow on the tree trunk, then if need be, move around the tree to your chosen photo spot to capture the image. On a rough barked tree such as a pine tree, make sure that the texture of the bark on the sunny part has not created half shadow.
If metering a building, meter off a corner so you get one wall in the sun and the adjacent wall in the building's own shadow. Alternatively, take a light reading off half the sunlit building and half the shadow on the ground.
When photographing the landscape I always take my own shadow with me. Yes, as long as the sun is shining my shadow will be there with me. I crouch down and take a light reading off the ground pointing the meter so half of it reads my shadow and the other half reads the sunny area. That's my light reading for the forseeable future, till the light changes. If I have any doubts about the average light reading, I take a reading from the shadow area and another from the sunny area, then see if my average light reading is in the middle.
Take a light reading Indoors
When photographing indoors by window light, be sure to take a light reading for the average of the subtle difference between light and shadow. This diffused, directional light, according to my view of the world, is the most attractive and useful light for photography. Although the level is low, the quality is high. Strive to meter it accurately.