F-stops and Aperture
Ansel Adams once said, “There are no rules for good photographs, there are only good photographs.”
While that sentiment is undoubtedly sweet, I have to respectfully disagree. Ansel, my man, you of all people know that there are certain rules that simply can't be ignored when it comes to cameras. Today I'll be going over one of the most important ones-- careful consideration of the aperture!
Image courtesy of nayukim on Flickr
What is this aperture you speak of?
Camera lenses are engineered much like our eyes — they are responsible for collecting light, arranging it into an image that makes sense of the world around us. The aperture is the diameter of the lens opening, and similar to our pupils, which open and close in varying situations of light, it is controlled by an iris. The larger the diameter of the aperture, the more light reaches the film or image sensor.
(Note: Many point-and-shoot or cell phone cameras have an automated aperture. Keep in mind that it is still important to understand what these mechanisms do in order to take advantage of their capabilities!)
How do I control it?
Aperture is expressed as F-stop and will be indicated on your camera in abbreviations that look like this: F2.8 or f/2.8
The "F" stands for the focal length of your lens, and the number indicates the diameter of the iris opening. When the aperture is opened up by one F-stop, the amount of light which reaches the sensor is doubled.
Image courtesy of Wikipedia
A handy rule of thumb is that the smaller your F-stop number (or f/value) is, the larger the lens opening (or aperture) will be. For instance, f/1.8 would be a large opening, letting in lots of light, and f/22 would be a tiny opening, letting in barely any light. Make sense? I know, it's a little tricky. Let's tune into our pal --jL for a break down:
Okay, so what does it affect?
Along with the shutter speed, the aperture size manages the film or image sensor's magnitude of exposure to light. In most cases, a fast shutter speed will require a larger aperture in order to provide sufficient light, and a slow shutter speed will require a smaller aperture to avoid overexposure.
The aperture also performs a critical function for focus. As the aperture decreases in size, the background and foreground gain sharpness. This zone of sharpness is called the depth of field. A large depth of field means that most of your image will be in focus regardless of its distance from your camera, and can be achieved with an F-stop of something like f/22. This is a popular technique for landscape photographers.
However, if you open the aperture to a wide setting like f/2, you will create a shallow depth of field. Foreground and background will have a soft focus, and the middle region and objects will be sharp. This can sometimes create a more dynamic composition, luring the eye to specific areas and separating the subject from their surroundings. You'll see this technique often in portrait photography, for instance.
But don't take our word for it!
Grab your camera and start playing around with your F-stop settings. After all, the best way to learn is through good ol' fashioned trial and error. But be careful! It's addictive.