Vincent's Lens Tests for:


In the PHOTO Techniques May/June 1997 issue, they dedicated three articles on the Japanese term, BOKEH (actually spelled BOKE but pronounced BO-KEH). A term used to describe the portions of the photograph that are not it focus, the fuzzy or blurry parts. It is usually these parts of the picture which distinguish the "look and feel" or "signature" of different types of lenses.

Good bokeh can be seen in the natural, smooth and coherent way the out of focus objects in the photograph are presented. The blurry blobs should mantain its basic shape and tone. Bad bokeh is when the out of focus blobs are presented in a DISTRACTING way. This can be seen as "jumbled shapes, choppy patterns of light and dark". A common example is the out of focus "donut" blob of a specular highlight, usually associated with mirror lenses, or the double images seen in the bokeh of some lenses. Having said this, what specifically is good and bad bokeh is, of course, a matter of personal opinion.

The following pictures demonstrate the tests that I have done on some of my lenses, specifically for the "bokeh" of each lens. Each photograph was taken on the same day, on the same roll of film. B&W film was used to eliminate any influences due to colour. All photographs were printed a grade 2 contrast. Sorry about the poor quality of the pictures, as I was trying to balance file size vs. getting the message across.

50mm, f/1.8 lenses

(all pictures - 1st: wide open, 2nd close up at wide open, 3rd close up at f/5.6)

Canon FL 50mm f/1.8 - 6 bladed diaphragm

Canon EF 50mm f/1.8 II - 5 bladed diaphragm

Rollei Planar 50mm f/1.8 (under Ziess license ) - 5 bladed diaphragm

Comments - Notice in the close up pictures of the Canon FL lens, their blobs are uneven, with a donut type specular highlights as well as double lines for some of the trees. Even at f/5.6, the background image wasn't coherent. I considered this to be bad bokeh. The Canon EF and Plannar lenses had very similar bokeh. This was surprising until I looked up the Canon EF lens design and compared it to the Planar. (They are nearly the same! see diagram below) The bokeh for these lenses is smoother, with the image starting to come together at f/5.6.
Figures from: 1) Rudolf Kingslake, A History of the Photographic Lens - 2) Canon, Lens Work II

Various Point & Shoot Cameras

(all pictures - 1st: wide open, 2nd close up at wide open, 3rd close up at f/5.6)
Agfa Apotar 45mm f/2.8 - 5 bladed diaphragm

Rollei Tessar 35mm f/3.5 (under Ziess license ) - 5 bladed diaphragm

Comments - I have never seen as much coma on any camera before I used the Agfa Apotar! Notice how the blobs are brighter on the bottom than on the top. Even at f/5.6, lens distortions are still very noticable. Its bokeh is very distracting to the photograph. (Good thing I only paid $5 for this camera at a garage sale) The Rollei Tessar, on the other hand, has a smoother bokeh, with the image comming together nicely at f/5.6.


Canon USM 70-210 f/3.5-4.5 - shoots at 70mm

Canon USM 70-210 f/3.5-4.5 - shoots at 210mm f/5.6 (just for fun)

Comments - As a zoom lens, the bokeh at 70mm is a little uneven. Just for fun, the shoot at 210mm shows how you can get too much of a good thing! But then again, you usually don't shoot at 210mm, wide open for its natural look.