Pixiq

The aperture is essentially a variable hole that's located inside the lens of your camera. This "hole" is formed by a series of overlapping blades. On an SLR or DSLR you can adjust the aperture using the dials and on compact digital cameras the aperture controls are often found hidden in your menu depending on the camera.

When adjusting the aperture the hole either opens wider or closes in tighter. This controls how much light is allowed to hit your digital sensor or your film.

The smallest number on your lens represents the widest aperture. This can be any number from 1.2, 1.4, 2, 2.8, 4, or 5.6 with many zoom lenses having a variable aperture of 4-5.6. These are called f-stops and when shooting at your smallest f-stop it's often referred to as shooting wide open.

Of course you can go the other direction called stopping down. This is done by increasing your f-stop number thereby decreasing the size of the "hole" or aperture. Common large f-stop numbers are 16, 22, or 32.

Back in the older (and not forgotten) days of film the aperture was used primarily as a means of getting a "correct" exposure. If you were in a situation where you needed more light you would open up your aperture (smaller numbers) to let more light in. Conversely, if you were in brighter situations like sunlight you would stop down (larger numbers) to limit your light input and avoid blowing out highlights. All of this was done in an effort to control light without affecting the speed variable so that moving objects would still be sharp.

While that school of thought will still help you get a more correct exposure I think that the digital photography world of today has a more creative use for aperture.

What changed?

The ability of photographers to vary their ISO has made the aperture control one of the most creative tools that photographers have in making compelling photographs.

Because we are no longer stuck with a predetermined film speed we have more control and options. Now we can set our aperture where we want and adjust the ISO or the shutter speed to control depth of field.

What is depth of field?

Depth of field can be thought of as the area (near to far) of the photograph that is in sharp focus.

Landscape photographers often require a large depth of field to capture images that have sharpness from the foreground objects in their photos to the far off mountains in the distance. This requires a larger f-stop or smaller hole.

Portrait photographers tend to want their subjects to stand out against a background that doesn't draw too much attention away from their subjects. This can be accomplished by using a more shallow depth of field. Using larger apertures (smaller f-stops) a photographer can throw a background out of focus easily.

The Three Factors of Depth of Field

• Focal length of the lens
• Distance between subject and camera
• Aperture

While focal length and distance do play important roles in depth of field I find that controlling your aperture gives you more freedom. So let's look at how and why aperture affects depth of field.

A lens, in theory, is really only supposed to focus on one subject (or distance) at one time. This distance is your focal plane. Ideally you want your main subject inside the focal plane for sharp images of your subject. But you can control the size of your focal plane with the aperture. Remember that larger apertures (f1.2, f2.8, or f4) create smaller areas of focus and smaller apertures (the larger f-stops 16, 22, and 32) create larger areas of focus.

In attempting to explain why this works this way photography teachers have used many different analogies. A common one is water flow. If you pour water out of one bucket into another bucket through a funnel (small hole or large aperture) you get more control and the water doesn't splash along the sides of the bucket. If you take that same amount of water and pour it into an empty bucket without the aid of a funnel (wide open or smaller aperture) you'll splash all over the sides of the bucket. This "splash" is representative of the light scatter that causes the blurriness in the image.

When light is allowed to pass through a smaller opening in the lens you'll get a larger area of focus because light didn't splash all over the sensor. This "cleaner" photograph gives you more detail.

More detail doesn't always mean a better photograph!

Remember that subject matter and story often times drive how a photographer uses aperture to help shape their image. This will differ from image to image.

Play around with different apertures and find what works best for your subjects and shooting style.

Photographs:

Aperture by Naka7a

The Wall & The Tor by andy_AHG (AHG Photography)

Golden by CMagee2010