Mastering exposure bracketing

A common technique in the days when traditional film photography was still king was something called exposure bracketing.The name sounds horrendously complex, but in fact the concept is simple.The idea is that if you're in tricky light conditions, where you think the camera's automatic exposure settings might be fooled and get it wrong - when you're shooting with bright light in the background, for instance, or shooting a very dark subject - you take more than one exposure. First, you take the one the camera thinks is correct, then usually two more - one with negative exposure compensation applied, and one with positive compensation. The idea is that, unless the camera really has things wildly wrong, by spreading the risk over three exposures one of them is likely to be correct (or close enough that It's salvageable).

Most digital SLRs - with the exception of the least expensive entry-level models - have an automatic exposure bracketing mode. You set the amount of compensation for each shot via the menu system and put the camera into burst mode. Now, when you hold down the shutter, instead of continuously firing, the camera will take three shots, automatically setting the exposure compensation to bracket the exposures. Some DSLRs (such as the Nikon D80 shown here) also allow you to take just two shots - one uncompensated and one either under or over. You can also usually combine bracketing with exposure compensation, to bump up the whole set of three exposures. That means you can take three shots, all of which can be either under- or overexposed. This can be useful if you want to reel off a quick sequence to use in a composite HDR shot (see pi 46). If you use exposure bracketing frequently, it's worth checking out which cameras have a dedicated exposure bracketing button, so you can engage bracketing mode simply by hitting the button and turning the selector dial to set the amount of compensation - the Nikon D80, for instance, has one.

when to use exposure bracketing The prime candidate for employing exposure bracketing is in situations where you won't necessarily have time to check your exposure between each shot, such as candid photography and

The -1EV frame (left) turned out correctly exposed with plenty of detail. If we hadnt taken the bracketing sequence, the shot would have been difficult to save.

The uncompensated frame (left) shows blown-out highlights, and the +1EV frame (above) is clearly much worse.

The -1EV frame (left) turned out correctly exposed with plenty of detail. If we hadnt taken the bracketing sequence, the shot would have been difficult to save.

This squirrel monkey stayed still long enough for us to get a bracketed sequence.

It s just as well, as the camera became confused and overexposed the middle, uncompensated exposure.

The uncompensated frame (left) shows blown-out highlights, and the +1EV frame (above) is clearly much worse.

Digital SLRs sometimes offer a dedicated button to set exposure bracketing without resorting to menus.

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A top-mounted i LCD panel shows at a glance thai bracketing ยก5 switched on. I

DSLRs, high-end compact models and superzooms will all usually offer exposure bracketing,

CUSTOM SETTING MENU

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outdoor events. It's a useful safety net to stop you getting home with what you hoped was the shot of your life, only to find that it was exposed incorrectly.

what should the bracketing be set to? If yOU habitually use exposure bracketing in "safety net" mode, you're essentially trying to guard against the camera getting things pretty wrong. That means your bracketed exposures should be a long way from what the camera judges is correct. A good base setting is to go +1EV (plus one "stop") and -1EV (minus one "stop") over and under. There's a benefit to this: if the underexposure is fairly extreme, it can also help with shots in low light; when you're busy just trying to get the shot and not looking at the exposure times, sometimes the "correct" exposure is too slow to handhold the camera, but the underexposed shot is just fast enough to capture the shot without too much camera shake. In this situation, even though the exposure isn't ideal, you may be able to rescue the underexposed frame in software (particularly if you're shooting in RAW mode - see p74), and get a better end result that's free of camera shake. This is equivalent to the film photographers' old trick of underexposing to catch the shot and instructing the developers to compensate with the chemical process when producing the negatives.

the drawbacks The obvious situation where exposure bracketing isn't ideal is with sports or action photography. If you're using burst mode to try to get as many shots as possible to capture that magic moment, exposure bracketing will just get in the way. If you have limited space on your memory card, you also won't want to use exposure bracketing - at least not habitually-since taking three exposures for every composition, only one of which you'll ever use, effectively cuts your storage space by two-thirds. It can also be annoying if you forget you're in bracketing mode and take just one shot, then move on. The next shot you take will be wrongly exposed, since the camera will still be in the middle of a bracketing sequence.

other types of bracketing Exposure isn't the only setting you can bracket: most cameras that have exposure bracketing have a white-balance bracketing facility, too, although it isn't usually possible to combine the two. With white-balance bracketing, rather than under- or overexposing the shot, the two shots either side will be with the white balance set to a warmer (more yellowish) setting, and to a cooler (more blueish) one. If shooting in JPEG mode this can be a useful feature, since once the white balance is set in a JPEG shot it's hard to correct (see pi 21). It's less useful if you're shooting in RAW mode, as you can adjust white balance in a RAW file in a completely flexible way (see p74). Either way, if you're in doubt about your exposure, it's always better to go for exposure bracketing than white bracketing since you can't get back detail that's lost when a shot is incorrectly exposed.

ADVANCED SETTINGS

Vibration can be a problem with extreme close-up macro photography. You can reduce it if your DSLR has a mirror lock-up function.

BURIED IN THE MENUS OF MANY DIGITAL SLRs IS A RANGE OF SPECIALIST OPTIONS. HERE'S WHAT THE MAJOR ONES ARE USED FOR.

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