What is bokeh?
Bokeh is a Japanese word meaning blur or haze. In photography it means the aesthetic quality and feeling of the smooth, fuzzy, blurred, hazy, out-of-focus background or foreground not competing with the main subject. Bokeh could be defined as the way the lens renders out-of-focus points of light. Very subjective quality and difficult to describe. When you see it, you know it.
Bokeh depends on:
1. Large aperture of the lens: f/1.8. f/1.4, f/1.2
2. Focal length of the lens: 85mm, 105mm, 200mm
3. Nine diaphragm blade lens
4. Distance of subject
5. Distance of background
Some lenses have famously excellent bokeh, including Nikon 85mm f/1.4 D or G (The cream machine), Nikon 105mm f/2.0 DC (defocus control), Nikon 135mm f/2.0 DC, Canon 50mm f/1.2, etc.
Let us look at a couple of sample images.
f/1.8, 1/2500 sec, ISO 100, 85mm
Notice the smooth, blurred, pleasing background. The blur circles have smooth edges.
f/3.2, 1/320 sec, ISO 100, 85mm
Look at the nice fuzzy foreground and background here.
Here are some great sites for further reading:
In summary, Bokeh is a great photographic tool to make your pictures unique and