September 1, 2007

A: Aperture

Aperture. It comes from the latin word apertura, which means "to open".

The definition is "an adjustable opening in an optical instrument, such as a camera or a telescope, that limits the amount of light passing through a lens or onto a mirror."

What does that mean? Simply put: when you take a photo, it's the size of the opening in the lens.

It's a little like the iris of your eye. It opens up to let more light in, and closes to let less light in.

How do you refer to the size of the aperture? Most people refer to it in terms of an "f-stop". A larger aperture is normally f/1.8, f/2.8 or f/4. A smaller aperture is normally f/11 or f/16...all the way up to an f/22 (on most cameras).

Did you catch the twist? In photography, the larger apertures have smaller numbers. The smaller apertures have larger numbers.

But what, really, does aperture control?

The depth of field (DOF). It allows you to make an image where:
  • The subject is in focus, and the background is blurry. This would be a large aperture (f/2.8 is one I use commonly). Portraits or photos that focus on a specific item (like wedding rings, flowers, etc.) use large apertures.
    Larger apertures decrease the depth of field.
  • The subject AND the background are in focus. This would be a small aperture (f/11 or higher). You'll find that when taking photos of a big scene, like a landscape, you want everything in focus.
    Smaller apertures increase the depth of field.
Here are two examples from out on the boat.

the specs: ISO 100, F/16, 1/64 sec.

Everything in this image is in focus - from the waves to the distant trees to the boat in the background. Smaller aperture (higher number), increased DOF.

the specs: ISO 125, F/4.5, 1/2048 sec.

My feet. Chilling on the side of the boat. You'll see that the havaianas logo on the white strap is clear and sharp, but that the water behind it simply blends into the background. Larger aperture (smaller number), decreased DOF.

You control the aperture most easily by using the Av function on your camera. Most point and shoots even have them these days - not just the bigger digital SLRs. Try it...see if you can find the difference!

One example that I love is of Henry below. While both shots are at F/2.8, they have differing degrees of a blurred background. The first, I'm shooting from slightly above him, and therefore, the camera is seeing that there is a lot to focus on. It makes for 'less of a background' to blur. It just wasn't as blurry as I wanted it. I really wanted Henry to be the focal point of the photo - not what he's sitting on, not who's holding him up.

the specs: ISO 200, F/2.8, 1/400 sec.

How did I solve that problem?

Reframe the photo. Simplify the background.

I dropped down to his level - getting rid of the distracting background of the wooden planks, Dad's helpful hand, and bark behind him. By bringing the focus on him and shooting at his eye level, the background blurred out beautifully.

the specs: ISO 200, F/2.8, 1/400 sec.

Throughout the rest of the A to Z project, I'll be showing the specs for the photos that are used as examples. See if you can guess the apertures before you see the answer!

1 comment:

Anonymous said...

A - ah - Apature. Got it!

I will be reading each day, and if every day is goign to be as informative as today, I will end up learning lots. No pressure:)