The exposure of a digital photograph is affected by the camera's aperture, shutter speed, sensor ISO rating, and of course the amount of light in the scene being photographed. An incorrect exposure will turn an otherwise well composed wildlife image into something mediocre and at worst completely ruin a shot.

All digital cameras have an automatic exposure setting, so it may seem that exposure is something that is best left up to the camera. It's certainly true that in some situations your camera's automatic exposure system will produce properly exposed shots, but there are also many situations where it will not.

Automatic exposure systems only tend to work well when a scene and the subject animal consist mainly of mid-tones. This is because automatic exposure averages out the exposure of the scene as a whole, achieving an overall exposure equivalent to if the scene was a uniform mid-tone grey. Since virtually no real world scenes consist of purely mid-tone grey, this can mean that your wildlife photos may end up incorrectly exposed if you rely purely on your camera's default exposure settings.

Scenes that consist of mainly very pale colours will come out underexposed (such as a pale animal in the snow) and scenes with very dark colours will come out overexposed. Furthermore, pale animals against dark backgrounds may be overexposed and dark animals against pale backgrounds may be underexposed. Animals with pied markings such as puffins or magpies will usually have their white areas overexposed. Therefore it is often necessary in wildlife photography to adjust your camera's default settings to correctly expose your shots.

Exposure Settings

Prosumer and DSLR cameras have three main light metering modes available:

• Multi-Segment or Matrix - this is a camera's default automatic exposure mode. This divides the image into a number of segments and averages out the exposure for the scene as a whole. This mode can work well for frame filling close-ups of animals and for wider shots of scenes consisting of mainly mid-tones, but as explained in the previous section, this mode will often produce incorrectly exposed images when the scene has significant areas of extreme light or dark.
• Spot Metering - in this mode the camera bases its exposure value on a single point in the image (usually the centre of the image, but this point can be adjusted on most cameras). This is a useful mode for wildlife photography as it often can enable you to achieve the correct exposure for the subject animal. Spot metering should however be used with care as the light readings can vary significantly depending on where you point the camera - it is best to choose a point on your subject that has a mid-tone.
• Centre-Weighted - like multi-segment metering this takes an average of the scene as a whole, but in this mode more importance is given to the centre of the image in the averaging process, meaning that the camera tries to ensure the centre of the image is correctly exposed. This is another good setting for wildlife photography that unlike spot metering is less sensitive to variations in scene brightness. As centre-weighted metering still uses as form of averaging it can still however produce incorrect exposure if the centre of the image contains extremes of light or dark.

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