Bokeh Explained

Bokeh Explained

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You’ve probably heard people talking about the quality of the bokeh in a photograph.  So what exactly is it?

The term bokeh (from the Japanese word boke meaning blur or haze) describes the aesthetic quality and character of the blur in out of focus areas of an image.  The quality and appearance of the bokeh may be affected by the shape of the lens aperture, and also by how well the lens is corrected for spherical aberration.

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In out of focus areas of a photograph light spreads or diffracts into round discs, and these are the bokeh, also known as circles of confusion.  Depending on the light source which is in the out of focus area, bokeh can be subtle or dramatic.  Gently lit leaves on a tree thrown out of focus will create a soft, subtle bokeh for instance, while brighter lights such as traffic lights or neon signs will create a much more dramatic effect.

Although difficult to quantify, some lenses enhance overall image quality by producing more subjectively pleasing out-of-focus areas. Good bokeh is especially important for large-aperture lenses, macro lenses, and long telephoto lenses because they are typically used with a small depth of field.

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Bokeh is also important for medium telephoto "portrait lenses" (typically 85–150 mm on 35 mm format) because in portraiture photography, the photographer typically seeks to obtain a small depth of field to achieve an out-of-focus background and make the subject stand out.

Today a more liberal interpretation of bokeh is considered to be any out of focus background that enhances the image.

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If you’d like to take a photograph using bokeh, this is what to do:

1. You’ll need to set your lens to its widest aperture.  To do this, set your camera to aperture priority (AV mode), and then select your lowest f stop number – depending on your lens this will probably be around f2.8.  This will give you a shallow depth of field, so that areas behind your sharply focused subject can be thrown out of focus.  (For more about this, see my blog on 20th August).

2. Getting close to your subject will give the best results, and also try to have a good distance between your subject and its background - the further away your background is from your subject, the easier it will be to throw it out of focus and so obtain some pleasing bokeh.

3. It’s easier to get a shallow depth of field with longer focal length lenses, so a wide angle will not be the best choice for this exercise – try using the telephoto end of your zoom lens.

4. Use manual focus and make sure you are sharply focused on your foreground subject.

5. If you’re using bright lights to get some dramatic bokeh, you may need to bracket around your camera’s suggested exposure (for more about this, see my blog on 22 June)

Bokeh can look sensational in a photo, and  good bokeh definitely elevates an image from ordinary to artistic. Why not enter some of your bokeh pictures in our monthly photo competition?