Photography is ultimately about capturing light. Whether your camera is loaded with slides, film, or a digital sensor, it is light that records on the medium to create an image. Given that fact, it follows that if you want to take full creative control of the photograph you are making, you need to understand the light you are capturing and the way your camera receives that light. The best way to become comfortable with the elements of exposure and how they contribute to your final photograph is to spend time with your camera in manual mode. Most people find manual mode a bit daunting at first, but after reading this series of articles you will have all the tools you need to take charge of your camera.
You could just start clicking away and teach yourself everything you need to know about exposure by trial and error, but if you take the time to first understand the factors that make up our exposures, you’ll be off to a great head start. There are three exposure variables in photography- the shutter, the aperture, and the ISO. Changing any of these variables may give you the exposure you desire, but each will affect the photograph in a different way.
In this article we will be focusing on aperture and depth of field. The aperture is actually located in the lens, rather than the camera. Simply put, the aperture is the hole that allows light to pass through the lens into the camera. The aperture range varies from lens to lens, but for this example I’ll be using my Nikon 50mm lens which has an aperture range of f/1.8 to f/22. On this lens, f/1.8 is the largest sized aperture, and produces the shallowest depth of field. On the other end, f/22 is the smallest sized aperture, producing the greatest depth of field. At f/1.8, it’s possible to use a faster shutter speed and a lower ISO, but background detail is lost. If the background is unimportant to the image, it may be an advantage to use a large aperture to create a blurred background in order to draw the eye to the subject. However, if the background is significant to the image, or if there are several subjects at various distances to the camera, then a smaller aperture will better serve the photograph. At f/22 we get plenty of background detail, but we will be forced to use a slower shutter speed or a higher ISO. The correlation between aperture size, aperture number, and depth of field is one that confuses a lot of people, and understandably so. It seems like the larger apertures to correspond to the larger numbers! So, why is that the case? If you stop thinking in terms of aperture size and start thinking in terms of depth of field, it makes sense- the larger the aperture number, the larger the depth of field.
In the image above, you can see the sharp contrast between the largest aperture and the smallest one. With the large aperture f/1.8, the eye is drawn directly to the flower with the weedy surroundings fading into a lovely green backdrop. With the small aperture f/22, all of the detail of the surrounding weeds compete for the eye’s attention. In this example you can see how important the aperture setting is to the overall look of the photograph. I hope this article has helped to explain depth of field and why it is important. Next time you take a photograph, before you click the shutter, take a second to think about how much depth of field you want to include and set your aperture accordingly. If you are new to photography, try taking several photographs of the same scene using a different aperture each time. It’s a great way to get familiar with your camera!
Thank you!