Isolate Subjects & Create Creamy-Dreamy Bokeh

A question I am asked often by new photographers is how to get that "blurry background" and make subjects stand out. This is referred to as shallow depth of field (DOF for short) and is controlled by aperture.

Aperture is the term for the size of the opening of the lens to allow light through to the sensor. It’s personally my favorite way to control photographs (with a shallower or deeper DOF). Depth of field is how in or out of focus the background of your subject is.

To get a shallow DOF (the blurry background) you need to have a wider aperture. The wider the aperture, the lower the f-stop number. As this number increases, the aperture becomes smaller and the depth of field becomes deeper.

Aperture is measured as f-stops, and without going into a math lesson, just remember that smaller numbers are larger apertures. For example, f/22 is a much smaller opening than f/2.8. The wider the aperture (smaller number) the more isolated your subject will be because more of the background is blurred (referred to as a shallow depth of field).

So why does a larger aperture create a shallower depth of field? The over-simplified answer is that decreasing the aperture opening decreases the size of the circle of confusion so less blur is apparent and in contrast, larger aperture openings increase the circle of confusion allowing more blur to be seen. Google circle of confusion for a physics lesson. :)

My eye doctor shared something interesting, as he knows I am a photographer, and in many ways our eyes are like a camera. If you wear glasses, try taking them off and looking through a small hole in a piece of paper, you will be able to see much better through the small hole than you do with the naked eye, because you narrow your eye's circle of confusion. The same physics apply.

The images in the example above show the differences achieved by different apertures. These shots were not edited (only converted from RAW to JPG), and aperture is the only setting that was changed between shots. Note how the sidewalk, the green leaves, the metal railing, and the street below all change with each aperture adjustment.

So, what exactly is bokeh? Bokeh is the visual quality or "look" of the blur in the out-of-focus areas of an image. Smooth and eye-pleasing is almost always the desired result, and helps give your subject more prominence. Great bokeh can be achieved by opening up your aperture to create a shallow DOF, where background distractions and light blur into dreamy beauty.

This image was shot at f/2.8 to isolate these blooms from all of the blooms in the background and create a dreamy bokeh. The bright sparkles are sunlight peeking through the branches.

Knowledge of the effects of aperture can help you achieve the creative vision you have for your subjects and help you to focus your viewers attention where you want it to be.