Spherical

A spherical lens puts no signature on the picture. Highlights stay round, flares scatter the way light scatters, and the frame renders evenly from the middle out to the corners.

Most of what an audience has ever watched is spherical, which is why it reads as neutral. Naming it is usually a way of ruling something else out.

The elements are symmetrical around the axis, so the lens projects the scene onto the frame without compressing one direction. No squeeze means no unsqueeze in post.

Aspect ratio comes from the crop rather than the glass. A spherical lens can deliver 1.85 to 1, 2.39 to 1 or anything else, because the frame is chosen at capture or in the edit.

Out of focus rendering depends on the aperture blades. A rounded iris gives round bokeh wide open and slightly polygonal bokeh when stopped down, and none of it stretches.

Use it for documentary, for realism, and any time the optics should carry no comment of their own.

Name it when a prompt might otherwise drift anamorphic. A request for a cinematic wide frame often returns blue streaks nobody asked for.

Anamorphic squeezes the image and leaves oval highlights and a horizontal streak on every bright source. Spherical does neither.

The bokeh is the test. Round highlights mean spherical, whatever the aspect ratio of the frame.

The model adds anamorphic artefacts anyway, because cinematic and anamorphic are tangled together in its training. Say round bokeh, no anamorphic squeeze, no streak flare.

The other failure is a lens with no character at all, rendered clinically. If you want film glass instead of a clean digital look, ask for it separately.