Aperture in Photography pt.1

Aperture, in my opinion, is one of the simplest things to set apart a great photograph. In this first of a two part series I will talk about aperture, what it does and how it works. Part two will cover what you should do with aperture and how to use it effectively with both an SLR and a point-and-click camera.

What aperture is

Aperture in photography is the opening in the lens which lets through light to reach the film or sensor. Inside the lens is a series of metal wings that make up a diaphragm that can be increased or decreased in diameter to let through more or less light. It works like the iris of the eye, contracting or expanding the pupil, or aperture of the eye.

What aperture does

The most important thing that aperture does is affect the depth of field of a photograph. Aperture can be adjusted to increase or decrease the depth of field so that the camera focuses on a very short depth with everything else out of focus or a very long depth, so that everything in the distance is in focus as well.

How aperture works

As I already stated, inside the lens is a diaphragm that opens and closes the aperture. With a large aperture, more light will be let in, but the depth of field decreases. This is because it affects how the rays of light shine through that hole. Normally, rays of light are bouncing all over in random directions. When rays are collimated, they are all straightened into a single direction. This is caused by a narrow aperture. Since it takes longer for light to go through the hole, more rays that are collimated from varying distances are let through and a larger depth of field is created. With a wide opening, not as many rays are straightened and only the rays that are focused upon with the lens will be sharp, thus a shorter depth of field.

Aperture on a camera

Aperture is indicated with an f-number. f-numbers range in value with the lowest ever used (to my knowledge) was f/0.7 in Stanley Kubrick’s film Barry Lyndon and ranging to f/128 or higher. The typical sequence is f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32 and so on. These are also called stops. The lower the number, the larger the opening and vice versa. So an f/2 aperture will let in much more light than f/32. In fact, each number larger will let in half as much light, so f/4 lets in half the light of f/2.8. In-camera adjustment tends to be finer than this and can do fractional stops such as f/3.2, f/3.5, and so on.

Lenses don’t use every f-number in existence. On the end of a lens, you can typically see what the lowest aperture is available with that lens. Lenses are either considered slow or fast. Fast being lenses with a lower number such as f/1.4 and slow being something like f/5.6 or higher. Typically, shorter (50mm or smaller) lenses are faster, though that is not always the case. You could have a 50mm lens that is much faster with f/1.4 than something like my 28mm with f/3.5. It depends on the construction, and ultimately the cost, of the lens. Faster lenses are quite typically more expensive.

The f-number doesn’t actually mean a specific hole size. It is actually a relative number, so that a f/2 on a 50mm lens is vastly different from a f/2 on a 100mm lens. Despite the size difference in the hole, the same amount of light would go through to the sensor.

Make sure you subscribe on the left so you don’t miss my next post showing you how to take this information to your camera and get a great photo using aperture.

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© This article is copyright of Chris Lane Photo and should not be found elsewhere.

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Tags: aperture, depth-of-field, f-number, f/, lens, light, photography, SLR
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