What is the right exposure? This question comes up often, especially when wondering whether the camera’s meter and automated mode has let us down. As Bryan Peterson writes in Understanding Exposure: “…[exposure] comes up most often as part of a question — a question I’ve heard more often than any other: ‘Hey, Bryan, what should my exposure be?’ … And my answer is always the same: ‘Your exposure should be correct!’”
“Correct,” Peterson goes on to demonstrate, depends entirely on what you are trying to accomplish. In fact, right after this quote he shows a “correct” exposure where the subject, a man, is in shadows but well exposed while the background is severely blown out. Oh, my, what would the Matrix-metering detractors do with such a shot if their Nikon D80 or D90 had exposed likewise?
To illustrate the challenges that both photographer and in-camera meter face, let’s look at an example where, with a much maligned D80, we placed the focus point on the subject, we set the aperture to f/8 and ISO 100, and let Matrix metering give us the shutter speed. We snap the shot, and sure enough, just like everybody says, the background is blown.
Maybe we should spot meter on one of our usual suspects, moving the focus point around until it lands on some of that blue water in the background. We set the shutter speed accordingly and press the shutter, only to find that now the background is well exposed, but the vase is almost a silhouette.
Well, maybe we should spot meter on the vase and see how that turns out. We do that and discover the background is even more over-exposed that in the first photo.
You may start to realize that with this lighting situation and others like it, you, the photographer, will have to make a compromise. How you arrive at this compromise will depend on what is important to you in this image. Do you want a beautifully exposed background? Or is the foreground vase more important? In short, what is this image about?
You could say that it’s about the pretty blues and greens in the background. Alternatively, you could reason that the vase is the subject, and its surroundings, though necessary for the overall look of the image, are secondary. There, you made a choice. Now take it a step further: if the vase is what matters, how do you want it to look? You think about and decide that you like how the back lighting and how it shows off those nice amber hues.
With that choice, it looks like the second shot is the best compromise, but you are not satisfied. The bright background is really too distracting. If the point of this image is to portray the vase, you don’t want anything to take away from it. Do you have any alternatives? You do. One would be to wait until the sun goes down a bit and see if that helps us in the background. As you think about it, though, you realize that the vase will also get darker. That gives you an idea. You have to add light to make this work. If you used the exposure setting for the second sample above, but added some light in the foreground to bring out the vase, how would that work? Here’s one try, with bounced flash to keep the light as natural as possible. You see some improvement, but the nature of the lighting (front-lit vs. back-lit) doesn’t quite give you the look you want.
Another option is to select the first exposure, which thanks to Matrix metering’s inclinations, is over-exposed by +0.7EV in the background, and in ViewNX, pull the highlights down with -0.7EV compensation and push the shadows out with shadow protection. The result is acceptable, and very little noise has crept in the shadow areas.
Still seeking that perfect exposure, you decide to give HDR a try. HDR has gotten a bad name thanks to a slew of cooked up samples, but you are very conservative in how you use it, and achieve the following result with a 3-exposure bracket.
You may have noticed that in this discussion, we started with a question about what constituted the right exposure, which we went on to answer by other means, namely what made this a good photograph. And that’s Bryan Peterson’s point. You can’t know whether you have the “correct” exposure unless you first know whether you have the intended photograph. This is why metering often frustrates us. No algorithm in the world has been programmed with our personal intentions in mind.
As a final observation, perhaps you agree the last two images offer the best balance between lighting and the goal we set out to accomplish in this photo. But it took post-processing to achieve these results, and you may find that distasteful because for some reason you believe every shot should come out of the camera perfect and ready for prime time. I advise you to jettison such a view-point. When the lighting is tough, you will have to use all the tools in your kit, and you better have post-processing as one of them. In fact, with experience you may find that as you approach shots like these you will start making them with post-processing in mind.