The Photo On The Wall

Only rarely will someone print and display a photograph that is not properly exposed. So you have to make sure the combination of aperture, shutter speed, and film sensitivity matches the light on the object, scene, or person you are photographing.

But, there’s more to it than that. Some of the time the dynamic range of the light in front of the lens is greater than the dynamic range of the film or the sensor behind the lens. Take this photo of a colonnade at Mission San Juan Capistrano for example. The image is exposed properly as far as the computer in my camera is concerned. But anybody can see that the sky is an overexposed white blob and the ceiling in the colonnade is so underexposed that there is absolutely no detail. In these cases you have to choose what part of the photo will be properly exposed. You might choose to emphasize the highlights and loose whatever detail is in the shadows. That is a good thing if you want to make a sillouette, but a bad thing when you think you’re photographing Aunt Mary with the sunset in the background and it turns out that you can’t see anything but her outline superimposed on a beautiful orange sky. I don’t know your Aunt Mary, but mine wouldn’t appreciate a photo of her sillouette. Alternatively you may decide to preserve the shadow detail and sacrifice the bright areas like most of my vacation pictures that have white space where the sky should be. Or somewhere in between.

There are several ways to address this dilemma. One way is to rely on your camera’s internal meter and hope everything comes out OK. You may get lots of good shots this way, but I doubt you’ll get a very high percentage of the great shots that will end up on the wall. Another way is to use a spot meter and measure the different brightness levels in your scene. Then adjust the exposure so that the brightest part of the photo that you aren’t willing to sacrifice is at the top of the brightness your camera sensor or film can accept. I like this way better because it gives me more control (maybe I should say creative control – that sounds cool, doesn’t it?) over the way the picture comes out.

That’s not the way I do it, though. I bracket a lot. I nearly always carry a tripod with me so I can take the exact same picture three times with different exposures. I usually set it to take one picture at the proper exposure, one that is 1.5 stops underexposed, and one that is 1.5 stops overexposed. (This is using a digital camera. Back in the old days when I shot film, I would typically bracket plus and minus one-third of a stop.) Look at the two images here. The one on the left is overexposed to show the detail of the ceiling and the one on the right is underexposed to put the clouds back in the sky. In some extreme cases, I have been known to change the middle exposure and take another set of three just to increase the likelihood of getting great definition at every light level in the eventual print. That probably would have been a good idea in this case. It’s a good idea to check the histograms for all three images to make sure you are capturing the full dynamic range of the scene you are photographing.

Of course, having one OK image and two lousy images on my hard drive doesn’t do much but take up space. The images have to be combined somehow into one picture that has good definition at every exposure level. I know of a few ways to do this. One is to use Photoshop’s High Dynamic Range feature. It combines all the bracketed images into one. You can also squeeze more dynamic range out of a RAW image using Photoshop’s Camera Raw, the software that came with your camera, or some other conversion software. A third way, and the method I typically use, is layers and masking. Read why I like this method and how to do it in the High Dynamic Range post.