Aperture Priority, Shutter Priority or Manual Mode

One of the hard things to figure out after buying your first camera is when you should move out of automatic mode and into the more advanced options of aperture priority, shutter priority or manual mode. Well, my advice -- get out of automatic mode as quickly as possible and start working in aperture, shutter or manual mode.

Brief Explanation - Aperture, Shutter Speed, ISO

Now, there are three principles you need to understand before you can move out of automatic: aperture, shutter speed, and ISO.

Aperture

Aperture is the opening in the lens. When you press the shutter release button a hole opens inside your camera that allows your camera image sensor to see the scene you want to capture. The aperture that you select affects the size of that hole. The larger the hole, the more light that reaches the sensor and the smaller the hole, the less light that reaches the sensor. Aperture is measure in "f-stops." Large apertures are represented by low f-stop numbers whereas small apertures are represented by high f-stop numbers. An easy way to remember this -- the larger the number, the smaller the opening and the smaller the number, the larger the opening.

Aperture controls "depth of field." Depth of field represents the amount of your image that will be in focus. A large depth of field means that most of your image will be in focus. A small depth of field means that a smaller portion of your image will be in focus. Large apertures (small f-stop numbers) result in a small depth of field. Small apertures (large f-stop numbers) result in a large depth of field. An easy way to remember this -- the larger the number, the smaller the opening, the greater the depth of field and the smaller the number, the larger the opening, the smaller the depth of field.

Now, what types of photography tend to make use of large depths of field vs. small? Well, in landscape photography you generally will want the entire image to be in focus, so you will want a large depth of field. However, in portraiture or macro photography, you will want to use a smaller depth of field so that only your subject is in focus.

Shutter Speed

Shutter speed is the amount of time that the shutter stays open. Shutter speed is measured in seconds (or fractions of seconds). The bigger the denominator, the faster the speed (e.g. 1/500 is faster than 1/20). When hand holding your camera, you likely will use shutter speeds of 1/60th of a second or faster because it is difficult to use anything slower than this without getting camera shake. If you intend to use anything slower than this, however, you will need a tripod. Many cameras have image stabilization technology built into the lenses, which purports to enable you to use slower shutter speeds without introducing camera shake. However, be aware that this technology has its limitations, so do not expect to obtain a clear image on an overcast day at 1/30th of a second without a tripod.

When deciding what shutter speed to use, you need to consider whether anything in your scene is moving and think about how you would like to capture that movement. If you want to freeze movement in your scene so it looks still, then you will need a faster shutter speed. However, if you want to create intentional blur to show the subject is moving, then you will want to use a slower shutter speed. The actual speed you would choose in either situation will vary depending upon the speed of the subject and the amount of blur you would like to introduce.

Additionally, when selecting shutter speed you need to also consider the focal length of the lens you are using. Longer focal lengths will accentuate the amount of camera shake so you will need to choose a faster shutter speed. A general rule of thumb is to use a shutter speed with a denominator that is larger than the focal length of the lens. So, if you are using a 100mm lens, you will want to choose a shutter speed of at least 1/100th.

ISO

In digital photography, ISO measures the sensitivity of the image sensor. Basically, the lower the number, the less sensitive your camera is to light and the finer the grain. A low ISO number (such as 100 or 200) will produce crisper images with less noise (or grain) while a high ISO setting (such as 800 or 1600) will introduce more noise/grain into your images. Many cameras by default will automatically select the ISO in a given situation. I would strongly recommend changing this setting because most cameras simply do not produce useable images at high ISO settings. While the image might look perfect in your cameras view screen, the moment you download it to your computer, you will notice the grain and noise.

Generally, you will want to use ISO 100 as that will give you crisp shots with little noise/grain. However, you will also want to take into account the lighting, grain and any movement in your subject. If the subject is not well lit and you do not have a tripod, then you might need to increase the ISO so you can use a faster shutter speed and still obtain a well exposed image. The trade-off is that you will have more noise/grain in your images. However, if you have a tripod and the subject is not well lit, then you can continue to use a lower ISO setting because you do not have to worry about camera shake.

Putting It All Together

Aperture, Shutter Speed and ISO are the three elements of exposure and a change in one of these elements affects the others. Thus, it is important to understand each of these elements before moving out of auto mode.

When to Use Aperture Priority, Shutter Priority or Manual Mode

Now, to the part you have all been waiting for -- how you decide whether to use aperture priority, shutter priority or manual mode. Well, it should actually be pretty easy for you to figure out now that you understand the three elements of exposure.

• Aperture Priority: In aperture priority mode, you control the aperture and the camera selects the shutter speed. You want to use this mode when you want to control the depth of field. If you want the entire image in focus, then you choose a small aperture (large number). It is important to remember that at some point, as you increase the aperture, the shutter speed will decrease to ensure the image is properly exposed and, at some point, the shutter speed will drop too low for you to continue hand holding the camera.

• Shutter Priority: In shutter priority mode, you control the shutter speed and the camera controls the aperture. You will want to use shutter speed priority mode when you have a moving subject and want to control how that movement is captured. You will also want to use shutter priority mode if you are using a telephoto lens without a tripod (or have shaky hands) and want to ensure you do not introduce camera shake. However, be aware that when shooting in shutter priority mode, you have no control over the aperture. So while you might end up freezing the movement in the frame, it is possible the entire image may not be appropriately in focus.

• Manual: In manual mode, you control both the shutter speed and the aperture. I believe it is best to use this mode when you "have the time." So, for example, let's say you decide to go out and photograph a bridge, well, since the bridge is not going anywhere you can take the time to experiment with the aperture and shutter. You also want to use manual mode if you are shooting under the same conditions or same light over and over again. For example, if you intend to shoot the same night scene over and over, once you identify the appropriate exposure settings, set your camera to manual so you do not need to readjust between shots. Finally, you will also want to choose manual mode when your camera gives you bad results. Sometimes the camera is simply wrong and you will need to make the determinations for yourself.

I use aperture priority mode for most of my photography since I generally need full control over the depth of field. However, when I am using a tripod and photographing a stationary subject, I tend to prefer manual mode.

So, closing thoughts, take your camera out of auto mode and begin experimenting with aperture, shutter and manual mode. Your photography will thank you!