Mastering Exposure: Exposure Functions

EXPOSURE FUNCTIONS

Bracketing
Allows you to shoot additional shots either side of your chosen exposure to ensure you get it right

Metering
Matrix metering is good all around, centreweighted for portraits, and spot metering for subjects that are off centre

Exposure Compensation
When shooting in a location where the problem with the exposure will be fairly constant, this can avoid changing your exposure constantly

Monitor
All the menus are available here and also reviewing your histograms and highlight areas to check your exposure

AE/Exposure Lock
AE lock is useful for metering off-centred subjects. You can take your light reading from a specific part of the image before locking the exposure and reframing your subject. This ensures you are metering for your subject as opposed to the background

Control Panel
You will need to keep an eye 
on your settings here and through the view to ensure accurate exposure.

METERING SYSTEM
The majority of DSLRs will give you the choice of three metering systems: evaluative (also known as matrix, or multi-pattern), centreweighted and spot metering.

1. Evaluative/matrix metering divides the frame into sectors and measures light from each.

Evaluative is the most popular for general-purpose photography, as it measures the light in many sectors of the frame to identify the overall exposure. Evaluative metering is still prone to error but, owing to the many areas that it measures from, it is a good, general metering system.

2. Spot metering reads the light from a very small area of the frame, usually in the centre.

Spot metering works in a similar way to centre-weighted, but uses an even smaller percentage of the frame to meter from – usually a 1° circle in the centre of the frame. This gives you a greater degree of accuracy when the main subject contrasts in tone to its surroundings. By taking a precise reading from a specific are a of the frame, such as a face, you can use this as the basis for the overall exposure – and avoid the camera taking the background into consideration, as it would with evaluative and, to a lesser extent, centreweighted metering.

 

3. Centreweighted metering covers a wide area but is biased towards the cental area.

Centreweighted metering still places the greatest emphasis on the central area. This is the preference of manyportrait photographers because it bases the majority of the exposure on the subject.

THE MID-GREY RULE
You can start to predict situations that will fool the camera’s lightmeter and adjust any necessary settings to compensate for these before they happen. Lightmeters are designed to find the average exposure, and while this works most of the time to produce an accurately exposed image, certain situations can fool a camera into recording a scene inaccurately. When you point your lens at a scene, the meter averages the various colours, tones and level of brightness to a mid-grey. For the most part, the shutter speed and aperture recommended by the camera is based on reproducing this mid-grey tone.