Is Exposure Bracketing Obsolete?
Back in the days of film, checking that you had the right exposure wasn't possible until you got the results back. They might think they had it right, but to cover their bases, photographers often employed bracketing in tricky situations. But is bracketing still useful with digital?
In theory, achieving correct exposure is a basic matter of accurate measurement and arithmetic. It's science, man. But things are rarely so cut and dried in real life.
I'm reminded of an introductory chemistry lab class I took back when I was a freshman in college. All we did was measure amounts of various compounds, mix them together in water and precipitate out what formed in the beaker. We then poured the lot through filter paper and again weighed everything. It might have been more fun had I been able to come up with the correct final weight but invariably I was off. It was definitely science, but that doesn't mean I could get the right answers most of the time.
And my chemistry lab was under what were supposed to be controlled conditions, not the variable lighting and extreme contrasts encountered when photographing in the great outdoors. Maybe it's a stretch to even compare a college chemistry experiment with the photographic goal of good exposure, but there are parallels. Both should be doable if you are careful in your measurements and follow the correct procedures, but somehow neither is really all that easy.
To hopefully compensate for slight inaccuracies in their measurements, film photographers often employed bracketing, shooting somewhat above and below what they thought the correct exposure should be. If one of the shots came out badly, hopefully one of the others would come closer. And since you never really knew if your best guess was a tad over or a tad under the optimal exposure, you could hedge your bets by taking an extra shot on both sides of what you measured. Wasting the ones that didn't come out was a small price to pay if it meant that, in the end, you got the shot with the remaining one.
Think about my miserable chemistry lab experiences again for a minute. I turned in what I thought was the correct final answer only to find out I had missed the mark by too much and thus get a less than optimal grade. If I could have turned in two additional answers, one slightly above and one below what I thought was correct I might have done better.
All this was based on the common premise that, if there were an error in my chemistry lab calculations or in your exposure measurements, neither of us knew in which direction that error might be. Once you got the processed film back the answer would be obvious, but by then it would be too late.
But digital gives us the ability to know right then and there if we've messed up the exposure, and if so, whether we mistakenly shot over or under what we should have. The need to shoot exposures both above and below our best guess simply no longer exists. If we nailed the exposure on the first try, great. If instead that shot came out a tad underexposed we can open up the aperture a bit or increase the exposure time accordingly and shoot again. Or if that first shot was somewhat overexposed we can do the opposite and reshoot. There seems to be no compelling reason to do both if we already know which way we need to go to correct our mistake. Had I had such an insight in that chemistry class I could have fudged the numbers with a reasonable assurance that I would be helping my grade rather than hurting it.
Indeed, digital exposure changes the rules of the game completely. Since you can check the histogram after shooting, or look for blinking highlights if your camera supports this feature, you can arrive at a correct exposure within a few attempts even when starting from a complete guess. If the shot comes out pure black or white, you know you're far off. If it comes out only slightly dark or light, you're getting close. If at first you don't succeed, try, try again. And with each shot you know you'll be getting closer to your goal. No need ever to shoot an exposure that is further away from the target since you always know if you are over or underexposed.
So is bracketing completely obsolete now? After all, camera manufacturers still include a bracketing feature on most models. Some of this is due to plain inertia I'm sure. Long time photographers are simply used to bracketing their exposures and haven't stopped to consider whether this still makes sense. Often it really doesn't these days, but there are exceptions. Fast moving wildlife generally doesn't have much patience when you're taking their picture. Waiting for you to check the histogram isn't likely. Sometimes speed is of the essence and a camera can automatically fire off three shots at different exposures in the blink of an eye, assuming typical shutter speeds. High Dynamic Range (HDR) imaging techniques that allow you to digitally combine multiple exposures of the same scene can often make use of in-camera bracketing modes.
In other words, bracketing isn't really obsolete, but it has become more of a niche feature rather than a common tool for general use in tricky lighting. Some film shooters I used to know fell back on bracketing as a crutch even under lighting that wasn't challenging. Some digital shooters I know now still do. But when you stop and think about it, they likely no longer need to even if they might once have been able to justify doing so.