Bokeh and Background Blurring with Canon Lenses
This series of tests was run to evaluate the bokeh and background
blurring properties of many Canon lenses at f/2.8 aperture and wider that
are used in portrait application. Photos for each focal length were taken
with a Canon APS-C camera (EOS 400D Digital Rebel XTi) mounted on a tripod
with cable shutter release on the same evening. The blurred background in
the tests included printed materials and straight lines to assess blurring
properties of the lens at each focal length and aperture. Direct and
reflective (specular) light sources were included in the out of focus
background to assess bokeh and aperture diaphragm patterns where wide
aperture lenses have been stopped down from maximum aperture to f/2.8.
Bokeh (Boke) is a variably defined property or concept originating in Japan that has come to refer to the pleasing quality of the out of focus (blurred) areas of an image related to factors including spherical aberration and the shape of the aperture opening. Smooth, uniform, "aesthetically pleasing" blur is referred to by many photographers as "good" Bokeh whereas background blur which shows evidence of "ugly" shape and structure is "bad" Bokeh. Articles by Bob Atkins and Harold M. Merklinger on Luminous Landscape provide more detailed technical information and examples.
Since good bokeh, like beauty, is largely in the eye of the beholder, I show the photographs produced by each lens without subjective comment. Let the viewer be the judge of which lenses produce good bokeh and photographically useful blurring of backgrounds.
posted 20 June 2007, Last revision 21 June 2007
© 2007, William L. Castleman