Why can Sony A7 photos show “banded” or double-line bokeh with fast lenses?

Yes, it’s a real effect. The main cause is usually the lens, not the Sony A7 itself.

This look is commonly called nisen bokeh or double-line bokeh. It often comes from lens designs with overcorrected spherical aberration, where out-of-focus blur discs are brighter at the edges than in the center. That makes background blur look harder, more outlined, or “banded,” especially with busy backgrounds.

Why it seems common on the A7: these cameras are often used with adapted legacy lenses, and older lenses are more prone to this rendering than many newer autofocus designs. Modern lenses, especially those designed to better control aberrations, often produce smoother blur.

Background and shooting conditions matter too: certain textures and highlights can exaggerate the effect with almost any lens.

One community report also noted that on the A7, shutter behavior—especially electronic first curtain at very fast shutter speeds—can alter bokeh shape somewhat, with the effect becoming more noticeable from roughly 1/1000 to 1/8000 s. So the camera can sometimes contribute, but the primary reason is still the optical rendering of the lens.