Controlling Depth of Field with an Automatic SLR © Wendy Folse Jul 8, 2001 The previous article covered depth of field scales and how to use them for creative effects. We learned how to get the maximum depth of field for landscapes and how to reduce the depth of field in order to blur the background in varying degrees using the distance scales engraved on the barrel of the lens. Many people however, may have cameras that do not have these markings or they may be using one of the autofocus auto‐program cameras. While these types of cameras often do not allow the user total control over the settings, there are ways to create the same type of effects. This article will cover some of those techniques. If your camera has several preprogrammed modes then you have a variety of creative tools at your disposable. Learning how to use them and what they do will help improve your photography. In order to control the depth of field, it is necessary to have control over the aperture setting. If your camera has a program mode known as "aperture priority", this is the program to use. In aperture priority mode, the camera sets the shutter speed for whatever aperture you choose. Say you want to blur the background greatly and you know that you will need a large aperture such as f4 to get the desired effect. In aperture priority mode, you set the aperture to f4. The camera meters the scene and automatically sets the appropriate shutter speed based on the selected aperture. The aperture setting always has priority, hence the name. Another common mode is called "shutter priority". With this mode, the opposite situation occurs where you select the desired shutter speed and the camera automatically sets the aperture. With this mode, you will not have a choice of apertures so you have no control over the depth of field. This mode is most commonly used where speed is the most important aspect such as for stopping action, preventing camera shake with a long telephoto, etc. Do not use this mode when trying to get creative shots with a blurred or out of focus background. Many automatic slrs, or single lens reflex cameras, have icons that represent various modes. Each of these modes is set to provide an average scene under certain conditions. In these modes, the camera is controlling everything based on preprogrammed algorithms. They are most often designated by symbols such as a mountain for landscapes, a person's head for portraits, a flower for close‐ups, etc. While you may not be aware of the settings used for each program, it helps to understand the basic concept behind each one in order to better understand what the camera is doing. This way you can begin to control the camera instead of the camera controlling you. The copyright of the article Controlling Depth of Field with an Automatic SLR in Photography is owned by Wendy Folse. Permission to republish Controlling Depth of Field with an Automatic SLR in print or online must be Page 1 granted by the author in writing.
With the camera set on the landscape mode, usually designated by a mountain symbol, the depth of field is set to infinity. The camera is using the smallest aperture possible to get the maximum depth of field. The thing to be concerned with here is the foreground. Because the depth of field is set out to infinity, the focus point becomes critical. Remembering from the previous article that you have only 1/3 in front of the focus point and 2/3 behind the focus point it becomes necessary to decide just where to focus. The camera will focus for you, but where you choose to focus is the key. Since the camera is set to focus out to infinity and 2/3 of this distance is behind the point of focus, that is a long, long, long way. What about everything in the foreground? You have only about 1/3 of the distance in front of the focus point. Say you want take a picture of a beautiful landscape. There are a couple horses in the foreground, a barn in the middle, and a mountain range in the background. Do you point the camera and focus on the horse, the barn, or off in the distance at the mountains? You still have to think about the composition and your decisions will influence the outcome thereby giving you some control over the process. Another useful preprogrammed mode is the close‐up setting. It is usually designated by the symbol of a flower. This mode is the opposite of the landscape in that it uses a very large aperture to reduce the depth of field. If you can't use the aperture priority setting and still want to add some creative zing to your photos, this is the mode to use. Keep in mind that it is designed for close focusing and a very limited depth of field. If you were taking a picture of a group of people, this would definitely not be a good setting. On the other hand, if you are taking pictures of a bed of daisies or rows of tulips, this setting is perfect. Select a perfect blossom to focus on and insure that there are no distracting elements in front of it, and then press the shutter. This preprogrammed mode will give you some beautiful results once you understand how it works and how to work with a limited depth of field. The portrait mode falls somewhere in between and has a moderate depth of field. It is great for adding emphasis on your subject while slightly reducing the background without blurring it completely. This program is probably the most useful for the average snapshots. The trouble with the preprogrammed modes is that the degree of creativity is controlled by the camera and you can never be sure of the precise settings. In both the landscape and the close-up modes, the priority is still towards the aperture but it isn't possible to decide the exact degree of the effect. Maybe you wanted it a little blurrier are a little less blurry. When at all possible, work with the aperture priority for controlling the depth of field. If your camera doesn't have this option, then by all means try some of the other program modes. Here is a rough guideline of the approximate apertures possible in each program mode. In the landscape mode, the aperture is generally around f11 to f22. In the normal mode, the aperture is around f8 to f11. In the portrait mode, the aperture may be around f5.6 to f8. In the close-up mode, the aperture is around f2.8 to f4, with f4 being more likely. Keep in mind that this is not exact and it will vary with each make, model, manufacturer and lens. However, it is a good point of reference to help you understand how these programs work. On most automatic slrs, the standard lens is usually a 35-80mm zoom lens. A 50mm lens is considered a normal lens on an slr. With the above zoom lens, almost all automatic slrs have a 50mm lens. Why is this important? For those people who don't have a distance scale marked on the barrel of the lens, refer to the chart in the previous article on The copyright of the article Controlling Depth of Field with an Automatic SLR in Photography is owned by Wendy Folse. Permission to republish Controlling Depth of Field with an Automatic SLR in print or online must be Page 2 granted by the author in writing.
depth of field in order to get a better understanding of the distance ranges and depths of field possible at each aperture using a 50mm lens. While the exact measurements may change slightly, the relationships remain the same. Even if your camera doesn't allow you much control over the operating procedures, you can still improve your photography by learning the principles that govern the way the camera works. By learning to work with depth of field, you will have a better grasp on how to be creative and how to take some awesome pictures that you will be proud of for a long time.
The copyright of the article Controlling Depth of Field with an Automatic SLR in Photography is owned by Wendy Folse. Permission to republish Controlling Depth of Field with an Automatic SLR in print or online must be Page 3 granted by the author in writing.