At the most basic level exposure is the relationship between the ISO, aperture, and shutter speed. When you push the button on your camera in automatic mode, there are a fantastic number of calculations going on inside your camera’s computer. Besides autofocus, your camera is analyzing the lighting, scene type, the light reflecting off the subject, the dynamic range, the contrast, and boiling all that down to a single set of numbers by balancing a fantastic number of variables.

In the old days you did all those calculations with a light meter in one hand an exposure guide in the other and, even then, you bracketed just in case. When you nailed the exposure it was part art, part science and part pure, dumb luck.

Now all that’s over. The sensor and computer inside your Canon 5D MKII or Nikon D300 camera combine to create an imaging device that is, by historical standards, absolutely mind blowing. But, even today, exposure is part art. While your camera is incredibly good at the science, the art still has to come from you. Part of what makes photographers worth the money is knowing when to trust the computer and when to take over.

Take the scene above for instance, a father and son sweeping out the engine bay at our old fire station. That is a classic “meter cheater”, meaning the proper exposure does not yield the most artistic expression of the scene. The first thing the camera tried to do was activate the pop-up flash so it could light the foreground subjects. I had to override the computer and tell it to expose for the outside light and ignore the foreground.

My opinion is that full manual shooters are kind of an anachronism these days. Manual shooting is slow, even when you really know what you’re doing. Do it long enough and you can get amazingly good at dialing in the settings, but you’re missing out on a host of functionality the sophisticated programming in modern cameras affords you.  In controlled conditions, like a studio, you’ll be doing more manual shooting because the environment stays consistent.

More often these days, you’ll be telling the camera what you want to do either through soft menu settings or selectively managing certain components of the exposure. If you’re out shooting fast moving objects, you might tell the computer you need at least 1/500th of a second on the shutter speed and then let the computer manage the other settings.

You can tell the computer to make the exposure darker or lighter, to expose for a particular part of the picture while ignoring everything else, or to selectively change the contrast, color saturation, or sharpness. Knowing when to override the computer is one of the factors that go into becoming a great photographer.

In the old days that relationship was one way and dictatorial. You told the camera what to do all the time. Today it’s more of a cooperative relationship, more subtle. You and your camera work together. You do some things, the camera does some things. When you’re in a hurry, like chasing a story subject down the street outside the courthouse, or your camera is on the end of your monopod trying to get over the heads of the other reporters at a press conference, you trust the computer to do more because it can read a scene at the speed of light.

So, get out there and experiment with exposure and your camera menu settings. Use the AEB function (Automatic Exposure Bracketing) and compare the results. Experiment with aperture priority, shutter priority, and changing your camera’s presets. Do it until you can look at a scene and guess within an f-stop what settings your camera will choose.

Just because you don’t need to use all the manual settings all the time, doesn’t mean you don’t need to understand them.