Besides the basic auto and pre-programmed settings, all DSLRs and some point-and-shoot cameras have what are commonly referred to as creative modes. The two most used are Av and Tv. This article will cover these settings and how you can use them to increase your knowledge of photography and improve your images.
The two settings stand for aperture value and time value. In the first, you set the aperture and the camera sets the shutter speed. In the second, you set the shutter speed and the camera sets the aperture. With both of these settings, the camera will attempt to get a proper exposure based on your selection.
Before we get into how to use these settings, it would be helpful to gain some understanding of how these two basic things control how a picture is made. You may have purchased a point and shoot so you didn’t have to learn this stuff, but knowing a little bit about it will go a long way to making better pictures and understanding mistakes. Basically, a digital camera is a box that allows light to hit a sensor and store information. In past times, they worked the same way, but the light hit film instead of a digital sensor. The two things that control how the image looks are how long the light is allowed in and through how big of a hole. These are shutter speed and aperture, respectively. That’s it. Everything else is just bells and whistles.
The combination of shutter speed and aperture determine how much light hits the sensor. The right combination and you get a well exposed image. The wrong combination and your image is either over or under-exposed. But these two variables do more than just control exposure. Shutter speed also can freeze or blur motion. Think of a picture of your child swinging a baseball bat. Is the bat sharp and frozen, or is it blurred? This is a result of the shutter speed. Aperture on the other hand, controls what is called depth of field. This simply means how much of the picture is in focus. If you take a picture of someone with a forest in the background, is the forest in focus, or slightly blurred. This is a result of aperture.
So thinking about the picture you are about to make, you can decide whether shutter speed or aperture are more important and start with those two controls. In many cases, neither of these is important, so long as you get the right exposure. To get some experience and confidence in using these settings, it might be useful to experiment a bit and see the results. The nice thing about digital is it doesn’t cost anything to play around.
First, go outside on a day with decent light and find something you want to take a picture of. Put your camera in auto or P mode, whichever you are used to and take the shot. While taking the picture, pay attention to the shutter speed and aperture that the camera has set itself to. Now, move the setting to Av and set your aperture to the same aperture as in auto mode and retake the picture. Unless the light or your picture has changed, the shutter speed selected by your camera should be the same as before.
Next, start changing the aperture up and down to different settings. Notice how every time you change the aperture, the camera changes the shutter speed to compensate. See how the little pointer on the exposure scale stays in the middle? Keep changing the aperture up or down far enough, and the camera may no longer be able to maintain a proper exposure. This is because the shutter speed will have to become too fast or too slow.
Now do the same thing with shutter speed. Set it to the same setting as your original picture and start experimenting with different settings. You will find the same thing – the camera will change the aperture to try and maintain a proper exposure. Here you are somewhat more limited as the available aperture is controlled by your lens, where there are many more shutter speeds available, which is controlled by your camera.
When you are done trying all the possible combinations, upload these images to your computer and look at all of them. See when and if the picture changed. Is the depth of field different? Is there any motion in your image that is blurred in one image but sharp in another? Also look at when the picture begins to look too bright and too dark. Experiment often with these settings and you will get a feel on when to use which settings to vary the way your picture is captured.