Whenever you read a lens review, you’re almost certain to come across an evaluation of the ‘bokeh’ of the lens. …

Whenever you read a lens review, you’re almost certain to come across an evaluation of the ‘bokeh’ of the lens. It’s an aesthetic quality that can be difficult to define and quantify. Most definitions refer to the way the lens renders out-of-focus points of light or the ‘blur quality’ of out-of-focus backgrounds. The term comes from the Japanese word ‘boke’  (pronounced bo-keh),  which means ‘haziness’, ‘dizzyness’ or ‘confusion’.







Bokeh is generally associated with a shallow depth of field. This is easier to achieve with long telephoto lenses but is also an essential parameter in macro photography. Bokeh can also be important for portrait photography where medium telephoto lenses (typically 85″“150 mm in 35mm format) are generally used.

In all these situations, the photographer will normally use a shallow depth of field to focus the viewer’s attention on the subject by blurring the background. In most cases, this is achieved with a wide lens aperture, which creates a relatively shallow plane of focus. Background regions become out-of-focus as a result.

The appearance of the background blurring can affect viewers’ perceptions of the attractiveness of a photograph. The lens plays a vital role in determining how smoothly background tonality is rendered. Differences in aperture shapes and lens aberrations can cause some lenses to blur out-of-focus areas in a way that pleases the eye, while others will produce blurring that is distracting or unattractive.

The image format, lens focal length, selected aperture, camera-to-subject distance, position of the subject within the scene, and shapes and patterns within the subject can also influence bokeh quality. So can tonal relationships with respect to foreground and background brightness and colours within the subject.


Artificial Bokeh

Many recently-released cameras provide an in-camera effect that simulates background blurring. Some cameras can produce quite attractive results; others less so. In most small-sensor digicams and camera-phones, background blurring is achieved by moving the lens and sensor together while keeping focus on the subject. The end result looks more like motion blur than ‘proper’ bokeh.

Several image editors provide tools for producing background blurring. But most involve complex mathematical adjustments. The best simulations are produced by techniques like Gaussian blurring, which requires a fair bit of processing power and is never as effective as the real thing.

The Lens Blur tool in Photoshop can be fraught with difficulties because the inherent bokeh of the lens will influence the way the blurring is applied. An oval blur point will remain oval unless you smear out the background completely (which will create an unnatural result). It’s simpler and you’ll end up with more satisfying images if you get a lens with good bokeh and learn to use it effectively.