In a previous article (F-Stop is NOT an F-word) I explained the nomenclature commonly used for aperture is f-stop. Aperture and f-stop relate to the size of the lens opening.
As one of the three components of an exposure (shutter speed, lens aperture, ISO) aperture plays a vital role.
The primary use of aperture is to control the depth of field (the distance in front of and behind the subject that is in apparent focus) of a photograph and in part control the amount of light that is allowed to enter the camera through the lens. Ever see the subject in complete focus against a fuzzy background (bokeh)? The photographer used a large aperature (smaller f stop) to create that creamy background that makes the main subject of a photograph really stand out.
Also from the article (F-Stop is NOT an F-word) we discussed that the bigger the aperture/f-number is the smaller the opening which in turn results in a larger depth of field. If you were to set your lens to its biggest number the lens would be “fully stopped down”. Conversely, if you were to set your lens to its smallest number the lens would be “wide open”.
Now, having said all that let me also say the depth of field is not sharpness. What I mean by this is that just because you have a large depth of field doesn’t mean that the subject or subjects will be sharp.
Apparent sharpness can be influenced by factors that have nothing or little to do with depth of field, such as lens quality, dirty sensor or lens element, fog or haze in the environment, even down to camera shake during long exposures.
So if you want good separation of your subject from the back ground, set your aperture to a smaller number. Then, continue to adjust your aperture up or down until you get the desired results.
Below is a diagram showing the comparative size of full f-stop apertures.
As you can see from the below image series aperture is a powerful tool in your photographic arsenal. These photos were shot using a Canon EF 70 – 200mm f/2.8L IS USM lens.
About the Author
Ray Mabry has over twenty years experience in photography. He started in film and used black and white to capture images in architecture, landscape and abstract forms. In 2001 Ray, with his extensive computer technology and digital imagery experience, made a natural and seamless migration to digital. Whether shooting film or digital, Ray loves the freedom of creative expression that photography has to offer.
Ray has a professional photography studio, rmabryphotography.com, runs a blog www.rmabryphotography.com/blog/ and also co-organizes a Meetup group called the Sonoma County Photography Group, www.meetup.com/Sonoma-County-Photography-Group/.