Understanding the relationship between aperture and shutter speed will help you take full advantage of your DSLR, allowing you to have more fun capturing photos. The aperture is the size of the hole in the diaphragm of the lens. It is possible to view this device when you look right square into the lens of the camera. The aperture diameter (size of the hole) is denoted by a sequence of f-numbers. The DSLR’s digital screen will display the aperture size, as well.
The smaller the f-number, the larger the aperture (hole), and consequently, the larger the f-number, the smaller the aperture. Every time you widen up one step (f/5.6 to f/4, for example), you allow in twice the amount of light. Reduce one step, and you let in half the amount of light. For illustrations of the actual aperture in the lens and its relationship to the f-stop numbers, go to my site, the link is at the bottom.
Photo by Justin Kern; ISO 100, f/22.0.
Equivalent Exposure
OK, so we know that aperture is the size of the opening in the lens where light enters, but how do you apply it to capturing images? Photography is all about getting the correct quantity of light for a given picture. At f/22, which is a very small aperture, less light will hit the image sensor compared to a picture taken at f/1.4, which is a very big opening. Keep in mind, though, that this is assuming the shutter is open for the same amount of time.
But you can get the identical exposure at f/22 as you can get at f/1.4 by simply lengthening the shutter speed, which causes the shutter to be open for more time, allowing more light in. Aperture and shutter speed settings combined allow a desired quantity of light to be exposed to the image sensor. Different combinations of f-stops and shutter speeds can achieve identical results in exposure. For example, f/8 at a shutter speed of 1/30, which will open the shutter for 1/30 of a second, will result in the same exposure as f/16 (smaller hole) at a shutter speed of 1/8 of a second. This is known as equivalent exposure.
Artistic Control
Knowing that you can get the same exposure values using different combinations of f-stop and shutter speeds is one thing. Knowing when to use them is something else. Just because you will be able to get the same exposure does not mean that your image results will be the same. This is where the art of photography comes in.
Do you want a sharp image or some blur? Do you want everything possible in focus or just the subject? Once you decide the answers to these questions you can choose your settings for aperture and shutter speed.
Depth of Field
Shutter speed settings and the effects they have on your image are not too hard to understand. The longer the shutter is open (slower shutter speed), any objects that are moving in the field of the image will appear more and more blurred. Remember, though, that the subject doesn’t have to be the one moving to result in a blurred image. A slow shutter speed with a shaky hand can blur a picture as well. This is why a tripod is a good idea–and sometimes mandatory–for shots with slower shutter speeds. Aperture has an effect on something known as “depth of field”. The smaller the f-stop, which widens the diameter in the lens, the less depth of field. Consequently the bigger the f-stop, which shrinks the diameter of the hole in the lens, the more depth of field. The more depth of field, the sharper all objects in the field of view. With less depth of field, only the subject in focus will be sharp.
Photo by Christophe LEUNG; ISO 125, f/3.2, 1/250-second exposure.
Put it to Use
It is not difficult to start experimenting with aperture and shutter speed and start getting quality results. Even the least expensive DSLRs on the market today have the tools necessary to aid beginner photographers when it comes to taking pictures on settings other than auto. Decide what type of picture and effect you want.
For the first example, we will use a candid portrait of a person’s face. The desire is to have the face fill the shot and to be the main focus point of the image. To obtain this result, put your camera on Aperture Priority mode. This is a setting that gives you control over the aperture while the camera takes care of shutter speed on its own. Now that you are in control of the aperture, go ahead and open it all the way. Focus on the subject’s face and take the shot. In taking this shot, you have reduced the depth of field so that only your subject’s face is in focus, blurring most everything else out.
I will use a landscape photo for the next example. Landscape photos require maximum depth of field. Put your camera on Aperture Priority mode like the example above. But this time, close or narrow the aperture all the way. Now that the aperture is very tiny, the camera will compensate on its own by forcing the shutter to stay open longer to get the right exposure. The result of this can lead to a blurred image, so a tripod is recommended.
For a final example, I will use a sporting event. This time, utilize the Shutter Priority setting on your camera. Shutter priority allows you to set the shutter speed on your own while the camera compensates for exposure by setting its own aperture. A cool technique to try is to slow the shutter speed down and take shots of the subjects running, jumping, etc.. The trick is to follow the subject with the camera while taking the shot at a slow shutter speed. If you are smooth about it, you will get a result that shows the subject mostly in focus but everything in the background blurred with motion. This will give the sensation of movement and speed in the photo. It’s not easy to achieve desired results, so take a lot of pictures.
Photo by jason; ISO 100, f/11.0, 22-second exposure.
What you want to do is try out these different techniques as often as you can. Get used to taking shots on settings other than full auto mode. Only once you get comfortable with the different camera settings and the relationship between aperture and shutter speed will you start to unlock the full potential of your DSLR camera.
Happy shooting!
About the Author
This articles was written by Joe Watson from lrcamera dot com. “I practice photography as a hobby. I love to learn and write what I learn. I hope this helps anyone out there with a new DSLR camera.”
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