So "bokeh" is a term for "all the stuff that's not in focus".
Different lenses render these out-of-focus areas differently, and what exactly is out of focus in the background can affect the picture.
For instance, the regular lines of the fence behind the dog are not distracting, and the blurry circles of the Christmas tree lights strung on the fence add a whimsical touch...
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| Nikon D700 & 70-210mm f/4 |
Similarly, the regular pattern of the highlights on the expanded metal patio furniture behind this pup doesn't jar the eye unpleasantly.
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| Olympus E-3 & Zuiko 150mm f/2 |
Whereas the travel zoom on the D700 made a distracting hot mess out of the tree branches behind this cat.
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| Nikon D700 & 28-200mm f/3.5-5.6G |
The little 28-200 is super-compact, given the zoom range it covers, and the fact that it's a full-frame lens. Its design was a triumph for Nikon. But I'll be careful in the future of shooting wide-open with it if the background is blurry; the background behind the cat probably wouldn't be so jarring if I'd stopped down a little.
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