Anamorphic

Anamorphic glass gives a picture a set of marks that nothing else does. Highlights stretch into ovals, bright sources throw a horizontal streak across the frame, and the edges soften while the middle stays sharp.

Those marks read as cinema to most audiences, because the format carried decades of large scale film production. Naming it is a shorthand for scale.

The lens squeezes a wide image onto the frame horizontally, usually by a factor of two on 35mm, and the projector or the software unsqueezes it. The result is a 2.39 to 1 picture from a taller negative.

The squeeze is also where the artefacts come from. Out of focus highlights come back as vertical ovals rather than circles, and a bright light in frame flares in a long horizontal line, often blue.

Depth of field behaves as though the lens were longer than its marked length, so an anamorphic 40mm separates a subject more than a spherical 40mm at the same stop.

Use it for scale: landscapes, wide dramatic frames, science fiction and anything that should feel like it belongs on a large screen.

Leave it alone for documentary and for anything meant to look unstyled. The flares and the oval bokeh are a statement, and they undercut a frame that is trying to look found.

A spherical lens has no squeeze. Highlights render round, flares scatter without streaking, and the picture stays even from the middle to the corners.

Look at one out of focus highlight. Round means spherical. A vertical oval means anamorphic. That single check settles it faster than the aspect ratio does.

Jordan Cronenweth shot Blade Runner (1982) anamorphic, and the blue horizontal streaks across the wet night exteriors are the format announcing itself. Wally Pfister used anamorphic on Inception (2010) for the same reason: the oval highlights and the wide frame give ordinary rooms the size the film needs.

The model returns a widescreen crop with round bokeh, which is a spherical picture in a letterbox. Name the oval bokeh and the horizontal flare streaks explicitly.

The other failure is flare everywhere. Ask for the streaks to come from named bright sources, such as a practical lamp or a headlight, or the frame fills with blue lines that belong to nothing.