Written by T. Michael Testi
While taking pictures is easy, especially in this digital world, mastering the art of photography is not always clear and straightforward. There are a lot of variables to factor in and one of them is Depth of Field (DOF). The first barrier that usually makes people's eyes glaze over is that it is a mathematical calculation. It combines a number of different factors including the distance of the camera to the object being photographed, the focal length of the lens, as well as the aperture that is being used.
The ExpoAperture2: Depth Of Field Guide was developed to make this process much easier and much more accessible to the average user. While there are several versions, the one that I am reviewing is the combo pack which contains two ExpoAperture disks. The first covers standard focal lengths (15-135mm), and the second is for telephoto lens lengths (70-600mm).
ExpoAperture is a tool that will allow you to take control over depth of field and let you apply selective focus within your images. This guide will show you the relationship between focal length, focal distance, aperture, and the resulting depth of field and let you make the calculations you need quickly and easily.
Just what is an ExpoAperture disk? It was invented by George A. Wallace as a companion product to the ExpoDisk. Essentially, it is a small hand calculator made of durable plastic that can fit easily into your camera bag or shirt pocket so you can always have it with you.
There are two ways to use ExpoAperture. First is to determine the aperture that will produce your desired depth of field, or to figure your depth of field by your chosen aperture.
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.
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