Bokeh
And the reflex lens		Apr. 2003

 


Update of 28 November 2005: For an example of a fine bokeh with a Pentax reflex, look at the bottom two song sparrow photos.
 
Bokeh refers to the quality of the blurring of the out-of-focus portion of an image, and with reflex (= mirror) lenses, the bokeh is generally unfortunate. The blur consists of untold "donuts," round, circular patterns that distract from the overall image.

After my first experience with a third-party reflex lens (which I threw away after a few months), I avoided them for over 10 years, because no matter how good the main subject, the distracting bokeh can ruin the photo. Nevertheless, my being interested in Pentax equipment, I've been curious about the Pentax reflex 400-600mm zoom. It is easily light enough for a handheld supertelephoto lens, but what would the bokeh be like?

After purchasing the 400-600mm, I found out that its bokeh can be incredible.

And thus this comparison: The first photo is from my deceased 500mm reflex lens, and it has enough donuts to open a bakery.
 

typical reflex bokeh
 

The choice for a following photo was difficult, inasmuch as I haven't had the Pentax reflex long enough to get a butterfly. Do I choose a busy photo or one to illustrate how far a good reflex bokeh can go. Well, I went for the latter. The following isn't the sharpest pussy willow catkin picture I have ever taken, but look at that bokeh!
 
Pentax reflex bokeh and catkin
 

Note, however, that the Pentax reflex isn't completely free of "donuts." Look at my two dove photos. The top one shows some donut bokeh; the bottom one is very clean. I suspect that with the Pentax reflex, objects at a certain distance in the immediate background will produce unfortunate bokeh. I have no idea of whether this is due to a slightly out-of-focus shot or the construction of the lens.

The good news, then, is one can have a lightweight, supertelephoto reflex lens; the bad news is that Pentax no longer manufacturers this lens. However, there is always ebay.

Photography note: The first photo was taken with a Pentax P3 and a T-- 500mm f/8 reflex lens. The second was taken with a Pentax LX and the SMC 400-600mm reflex lens, probably at 400mm.



Peeking dove (Pentax reflex shots)   |   Sharp catkins (macro shots)

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