What is Aperture?
As most of you are probably already aware, an aperture is a hole or opening, and it is no different in photography. In photography when you use the term though you are referring to the amount the aperture ring inside the lens has opened to allow in light. The larger the opening the more light it allows in.
The measurement of this is literally referred to as the aperture and then its numerical value or f and the numerical. For example an aperture of 2.8 could also be referred to as f2.8. It is important to remember that the larger the aperture the smaller aperture number (or the larger number the smaller the aperture). So following this system of measurement f2.8 would be a much larger aperture than f22.
Different lenses also have different minimum or and maximum apertures and zoom lens can be have a fixed or variable aperture. Generally speaking the large a lens can open or the larger its maximum aperture the more expensive it is. These lens are also called “fast” or “fast glass” by photographers.
In zoom lenses, particularly in cheaper lenses, you may have a variable aperture. This doesn’t mean you can change the aperture, you can do this with all lenses. What it does mean is that when the lenses zoom in and out the aperture will change. In general this is undesirable for photographers but can make the lens cheaper to produce.
A fixed apeture means that matter how much you zoom in or out the apeture will not change (unless of course you decide to change it yourself).
How does it effect the Exposure?
Aperture most definitely effects exposure. The larger the aperture the more light is allowed to hit the sensor or film. Unfortunately, because the way aperture is measured we don’t gain or lose a stop of light every time it is doubled or halve for each stop of light like shutter speed or ISO do. There are however standard apertures and every time you move from on to the next a stop of light is gained or lost.
The standard apertures are 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32
What else does it effect?
In addition to effect exposure, aperture plays a major role in effecting an image’s depth of field (DOF). DOF is the portion of the image that is in focus and the amount of the image that is allowed to go out of focus. The large the aperture the more quickly things fall out of focus. So an image a f1.2 will likely have a very soft creamy background, whereas the same image shot f22 will have a background virtually completely in focus.
Still want to learn more?
Here’s a great video that goes fairly in depth, as well as giving you some ideas on how you could experiment with aperture yourself.