Bokeh and Wide Aperture: How to Get More Background Blur

Bokeh describes the quality of the out-of-focus areas in a photo, and the amount of blur is governed by four variables: aperture, focal length, subject distance, and the distance between subject and background. A wider aperture (smaller f-number, like f/1.8) creates a larger physical opening and thus a shallower depth of field. A longer focal length increases blur at the same aperture. Moving closer to your subject and pushing the background farther away both magnify the effect.

The aperture numbers, concretely. At the same framing on full frame, f/1.4 blurs far more than f/2.8, which blurs more than f/4. But aperture alone is a trap: an 85mm f/4 shot from 3m with a background 30m away will out-blur a 24mm f/1.4 shot from 0.5m against a wall. The most under-used trick is simply separating your subject from what is behind them - move the subject two steps forward and watch the background dissolve.

Shape and quality matter, not just quantity. Bokeh character depends on the aperture blade count: nine rounded blades give circular highlights, seven straight blades give heptagonal ones. Busy, nervous bokeh with outlined highlights is common in older zooms and mirror lenses; smooth, creamy rendering is what people pay for in an 85mm f/1.4. Specular highlights - string lights, sun through leaves - are the best test of bokeh quality.

Practical mistakes. Stopping down is often better: at f/1.2 the depth of field is so thin that the tip of a nose is sharp and the eyes are not. For portraits, focus on the nearest eye and stop to f/2-f/2.8 for a whole face in focus with a blurred background. Crop-sensor shooters should remember the same lens gives more depth of field than on full frame - a 50mm f/1.8 on APS-C behaves like roughly f/2.8 on full frame for blur purposes. And clean your front element; dust turns into ugly bright blobs at wide apertures.