Photography 101 - Depth of Field

I'm posting the first of what hopefully will be an ongoing category of tips on different subjects. This first one will cover a photography tip on how to use the aperture on a camera to creatively leverage depth-of-field in photographs.

Aperture and shutter speed control is Photo 101, which I unfortunately never took. How to use those basic principles to creatively to control depth of field is a new "discovery" for me and one of the most creative tools that photographers have.

Depth-of-field is, basically, the distance in front of and behind your subject that stays in focus. Let's say you're shooting a portrait of someone. Based on your decision, you can make the flowers in front of the person sharp and detailed or fuzzy. Same goes for the trees behind them.

So what does that do?

If you choose to let the foreground and background drift out of focus, you single out your subject and cause it to have the attention in the photo. If not, and the elements in front of and behind the subject stay in focus, then they become part of the scene to compliment your subject. Pretty nifty!

Depth-of-field is controlled by the lens aperture, the hole where light travels into your camera to the film or sensors on a digital camera. The aperture size, known also as the f-stop, is adjusted by a diaphragm that either closes down or opens the hole to control the amount of light coming in. Wide apertures, f-stops of smaller numbers such as f/2.8 or f/3.5, allow for less depth-of-field, keeping the subject in focus but not much else. Narrow apertures, bigger numbers like f/22, allow greater depth-of-field, so that the area in front of and behind the subject stay in focus. Small f-stop, less depth-of-field; big f-stop, greater depth-of-field.

When shooting at wider apertures, certain things become more important to pay attention to such as focus, shutter speed and ISO. Focus at wider apertures is critical, since small changes can dramatically shift what is in focus. Also, with a wider aperture to make the depth-of-field shallow, the shutter speed will be higher. The wide aperture and/or a high shutter speed may not enable enough light to reach the film or sensor. A higher ISO film or setting on your DSLR will increase the sensitivity to light.

Below are some test shots using shallow depth-of-field. All of these were taken in slightly overcast natural light without flash.