| The exposure of a digital photograph is affected by | | | | If you find your camera's metering doesn't produce |
| the camera's aperture, shutter speed, sensor ISO | | | | good results for a given scene (e.g. when your |
| rating, and of course the amount of light in the scene | | | | subject animal is very light of dark) you can use the |
| being photographed. An incorrect exposure will turn | | | | manual EV Compensation (Exposure Value |
| an otherwise well composed wildlife image into | | | | Compensation) setting on your camera to adjust the |
| something mediocre and at worst completely ruin a | | | | exposure it will use. For example, without EV |
| shot. | | | | compensation a spot-metered or centre-weighted |
| All digital cameras have an automatic exposure | | | | picture of a white swan is likely to come out |
| setting, so it may seem that exposure is something | | | | underexposed (as the camera tries to achieve a |
| that is best left up to the camera. It's certainly true | | | | mid-tone grey for the swan's white plumage). By |
| that in some situations your camera's automatic | | | | setting your camera to a positive EV Compensation |
| exposure system will produce properly exposed | | | | (you may need to use a little trial and error to find |
| shots, but there are also many situations where it will | | | | the exact amount of compensation required) you'll be |
| not. | | | | able to get a picture where the swan's plumage is |
| Automatic exposure systems only tend to work well | | | | exposed correctly. |
| when a scene and the subject animal consist mainly | | | | Another trick you can use to get the correct |
| of mid-tones. This is because automatic exposure | | | | exposure is to use the exposure bracketing function |
| averages out the exposure of the scene as a whole, | | | | on your camera. In this mode the camera takes |
| achieving an overall exposure equivalent to if the | | | | three shots at different exposure settings, one at |
| scene was a uniform mid-tone grey. Since virtually no | | | | the camera's recommended exposure, one slightly |
| real world scenes consist of purely mid-tone grey, | | | | underexposed and one slightly overexposed, |
| this can mean that your wildlife photos may end up | | | | increasing the likelihood that one will be correctly |
| incorrectly exposed if you rely purely on your | | | | exposed. It should be noted that as bracketing takes |
| camera's default exposure settings. | | | | multiple exposures it is not particularly suitable for |
| Scenes that consist of mainly very pale colours will | | | | shooting animals in action since the animal is likely to |
| come out underexposed (such as a pale animal in the | | | | move between exposures making each bracketed |
| snow) and scenes with very dark colours will come | | | | shot different, and unless you are very lucky, the |
| out overexposed. Furthermore, pale animals against | | | | best exposed shot might not be the shot with the |
| dark backgrounds may be overexposed and dark | | | | animal in the best position. |
| animals against pale backgrounds may be | | | | Checking For Correct Exposure |
| underexposed. Animals with pied markings such as | | | | You may be tempted to try and check the exposure |
| puffins or magpies will usually have their white areas | | | | of a picture after you have taken it by viewing it on |
| overexposed. Therefore it is often necessary in | | | | your camera's screen. While this may give you rough |
| wildlife photography to adjust your camera's default | | | | idea, it is not very reliable as a screen's brightness |
| settings to correctly expose your shots. | | | | can vary and the ambient lighting conditions can |
| Exposure Settings | | | | affect how an image appears on the screen. A far |
| Prosumer and DSLR cameras have three main light | | | | more reliable way of assessing exposure is to look at |
| metering modes available: | | | | your camera's histogram. The histogram is a graph |
| * Multi-Segment or Matrix - this is a camera's default | | | | showing the distribution of tones from light to dark in |
| automatic exposure mode. This divides the image into | | | | an image. For most shots you want a bell shaped |
| a number of segments and averages out the | | | | histogram with the majority of pixels towards the |
| exposure for the scene as a whole. This mode can | | | | middle of the graph, although this does not |
| work well for frame filling close-ups of animals and | | | | necessarily hold true for pictures that have significant |
| for wider shots of scenes consisting of mainly | | | | light or dark areas. |
| mid-tones, but as explained in the previous section, | | | | Another feature most cameras provide for checking |
| this mode will often produce incorrectly exposed | | | | exposure is an image playback mode where the |
| images when the scene has significant areas of | | | | massively overexposed parts of the image flash on |
| extreme light or dark. | | | | screen. Massively overexposed means a region of an |
| * Spot Metering - in this mode the camera bases its | | | | image is so overexposed that it has gone to pure |
| exposure value on a single point in the image (usually | | | | white - this is referred to as clipped or burned out. |
| the centre of the image, but this point can be | | | | Overexposure to the point where significant portions |
| adjusted on most cameras). This is a useful mode for | | | | of the image are clipped is something you should |
| wildlife photography as it often can enable you to | | | | avoid at all costs in your digital photography. Once a |
| achieve the correct exposure for the subject animal. | | | | portion of an image is clipped all information in that |
| Spot metering should however be used with care as | | | | part of the image is lost - nothing can be done in |
| the light readings can vary significantly depending on | | | | tools like Photoshop to recover it. It should be noted |
| where you point the camera - it is best to choose a | | | | here that it is fine to clip specular highlights, for |
| point on your subject that has a mid-tone. | | | | example caused by the sun reflecting in the animal's |
| * Centre-Weighted - like multi-segment metering this | | | | eyes, but clipping large areas of detail should always |
| takes an average of the scene as a whole, but in this | | | | be avoided. |
| mode more importance is given to the centre of the | | | | The problems associated with clipping mean that it is |
| image in the averaging process, meaning that the | | | | generally safer to slightly underexpose a digital image |
| camera tries to ensure the centre of the image is | | | | than it is to overexpose it, as this will retain more |
| correctly exposed. This is another good setting for | | | | detail in the highlights. Underexposed images can be |
| wildlife photography that unlike spot metering is less | | | | corrected easily in tools like Photoshop, but if an |
| sensitive to variations in scene brightness. As | | | | image is significantly underexposed the corrected |
| centre-weighted metering still uses as form of | | | | image will have an undesirable grainy texture called |
| averaging it can still however produce incorrect | | | | 'noise'. Slight overexposure can also be corrected in |
| exposure if the centre of the image contains | | | | Photoshop but only when clipping hasn't occurred. |
| extremes of light or dark. | | | | |