For example, say you are using a Nikon D200 camera. The first thing is to determine the sensor size; they give you a chart to look up the sensor size, and in this case it is 1.5x. You set your sensor size on the disk (the green #1 in the image). You then rotate focus zone dial to your lens focal length, in this case 200mm (yellow #2).

You next flip the dial over to find your subjects distance, say 13 meters (red #3). Then you choose your desired depth of field, in this case, 12 to 14 meters (red #4). You count the number of alternating gray and white zones covering this depth of field (gray #5). In this case it covers about one zone. You flip the dial back over and look for that zone number on the gray ring (gray #6), in this case it is one and shows f11 (brown #7). So that is your aperture. Determining the depth of field is handled in much the same way.

I found the ExpoAperture incredibly easy to use and understand. Once you get the steps down, it makes figuring out depth of field simple and much more accurate than ever before. ExpoAperture would be a great tool for the classroom, and in fact they make a large size that can be used in the classroom setting.

If you want to have better control of your depth of field, if you want to have a tool small enough to fit in your shirt pocket, if you just want to get it right, then you need ExpoAperture. At $39.95 USD, the ExpoAperture is incredibly affordable, and is usually available for much less if you shop around. I highly recommend the ExpoAperture.