Mastering Exposure: Tricky Metering: Back Lighting

Tricky metering:

BACK LIGHTING
A portrait taken in front of a window with a great view in the background sounds like a guaranteed scenario for a great photograph but, as with many scenes where the light is coming from behind the subject, the contrast range between your subject and the background is likely to be too great for the sensor to handle.

If the camera’s meter is influenced by the background, the subject will be too dark and, in some cases, even a silhouette.
To get a correct exposure on the face you’ll need to take a selective light reading, though of course all the background detail will then be overexposed.

The only way to balance the two is to increase the light level on the face (using either reflectors, or flash) to more closely match the background level.

BRACKETING
Bracketing allows you to shoot an additional exposure (or two) either side of your first reading, giving you a greater chance of obtaining an optimum exposure. The camera calculates the extra exposures based on your initial reading and by what increment you wish to bracket your shot by and takes a sequence of exposures at the different settings, in quick succession.




USING A GREY CARD
A grey card is the absolute middle value in a tonal range and is often referred to as 18% grey. Shooting a grey card as a test image allows you to find the centre-point for your exposure. This will also help in post-production when looking to correct exposure or to spot colour-casts in your monitor or prints. Here, we have used a fold-out grey card in the image to help act as a basis for the exposure.





OUR SET-UP
We used a tripod-mounted
camera and shot against a window looking out across London, using only available light.

Dark subjects
Lightmeters are programmed to pick an exposure that will record the scene as a mid-grey. Most scenes contain a mix of light and dark areas so this ‘average’ usually works, but there are some circumstances where it won’t. With subjects that are mostly dark the camera will try to lighten it to a mid-grey. Knowing this, you’ll have to override the camera to give the sensor less light than the camera wants to provide. The amount will vary depending on the tones in the scene.

Light subjects
Lighter-than-average scenes are a problem too. Examples include shots typically taken on holidays, such as beach shots or snow scenes, which contain large areas of brightness. Leaving the camera to its own devices will result in muddy, underexposed pictures as the camera tries to turn the beach or snow mid-grey. You’ll need to add more exposure than what the camera suggests. Again, the amount will vary according to the circumstances.