How to get good exposure with spot metering

When it comes to getting good exposure, we’ve all made plenty of mistakes. You know, like setting the camera for what you thought would be a good exposure only to find out the camera had something else in mind when you clicked the shutter. This happens to me all the time when I don’t stop to think about what I’m trying to accomplish, which is when my camera takes over and tries to figure it out for me. My camera is possessed sometimes, and I’m sure you can say the same about your camera.

Getting good exposure means understanding how your camera works, which is really quite simple. This is a good thing for simple minds like mine 🙂 . Anyway, your camera’s metering system thinks of everything as 18% grey. So if you meter off of something white and set the exposure to the middle where the camera says you have good exposure, the resulting photo will be underexposed and grey or dark. Inversely, if you were to meter off of something dark and set the exposure to the middle like your camera is telling you to do, the resulting photo will be overexposed and washed out. Why, because the camera wants to adjust the white or dark you are metering off of to 18% grey. Why 18% grey, if you divide black to white in ten steps, the middle block will be about 18% grey. Incidentally, this division of black to white is what Ansel Adams did to create the Zone System.

As it turns out, the Zone System can be very helpful in getting good exposure on a digital camera. However, to do so you will need to be in spot metering mode. Why spot metering you may ask, why not matrix metering? Well let me put it this way, in matrix metering, the camera looks at a number of areas within the frame and meters them, then it takes this information and chews on it, wads it up, stomps on it, meshes it together, runs it through some voodoo (see the camera’s really are possessed), pushes it through the wringer, and processes it through several black boxes of magic that require a top-secret clearance to even look at…and then decides what the best exposure is after considering a number of factors from each area metered. If you want your camera to make exposure decisions for you, then you can use matrix metering. Now before the flood of hate mail starts, let me just say that I’m not against matrix metering. It has it’s the purpose, but as I’m going to show you, in difficult lighting situations, spot metering is a better choice. Why, because spot metering is just what the name implies. It meters only a small area around the focus point only and is not influenced by all the other lights and darks within the frame. This means you have more control, and with that control, you can apply simple adjustments to what the camera thinks is a good exposure and actually come up with a good exposure! This means an exposure that is based on what you want, not what the camera wants. Let me show you a couple of examples.

In this image, I used spot metering and metered off the bed rail which is on the dark side of things. Now considering I didn’t want this part of the image to be lighter than it is, I set the camera’s exposure to what it thought was a good exposure, then applied the zone system to this and adjusted the exposure down a stop (-1ev). The key thing here is when metering off of dark items or objects, adjust the exposure down, and when metering off of light items or objects, adjust the exposure up. I then framed the image for composition and took the shot. The result is what you see here. As you can see, detail is retained throughout the image and the mood I felt when entering this room is captured.

You might be asking, so why only 1 stop, why not 2 stops or more. Well the answer to this is found in the zone system developed by Ansel Adams, wherein he determined the exposure adjustments for certain objects. So with the application of a little knowledge in applying the zone system, and a lot of trial and error (and I do mean a lot), you will get to a point where you just know how many stops to adjust up or down.

In this next image, I spot metered on the white of the fireplace just above the mantel. Since I wanted this white fireplace to remain white in the final image, I adjusted the exposure up 2 stops and took the shot.

As you can see in this shot, some of the darker areas where compromised and detail was lost. Even so, the mood of the shot is retained and the lost detail didn’t matter to the overall shot anyway. There will be times when compromises will need to be made, and when you just can’t live without all the detail to create that masterpiece – then there’s HDR.

For more information on the zone system, do a google search for “zone system” and have fun reading!