What is the difference between shallow focus and bokeh?

Shallow focus is the choice to keep one plane sharp. Bokeh is how the out of focus area renders, and it only becomes visible when there are point lights or bright highlights behind the subject.

When should I use shallow focus?

For close work on a face, for lifting a detail out of a crowded background, and for any location you would rather the audience did not study.

How do I prompt shallow focus?

Ask for a wide aperture and a thin plane of sharpness, then name the one thing that must be sharp. Without that the focus lands somewhere near the subject rather than on it.

Shallow Focus

Selective focus
Faible profondeur de champ

Only a thin slice of the scene is sharp.

Run this shot

Opens a video model with the prompt in it. The price is on the page before you sign in.

Shallow Focus: Only a thin slice of the scene is sharp.

What it is for

One thin slice of the scene is sharp and everything else falls away. The frame makes the choice for the audience, which is why the look reads as intimate even when the subject is doing nothing.

It also hides things. A cluttered room, a crowd, a background you cannot control: all of it dissolves into tone, and the shot becomes about the person.

How it works

Depth of field shrinks as the aperture opens, as the lens gets longer and as the camera gets closer. An 85mm at f/1.4 on a full frame sensor holds a band of sharpness a few centimetres deep at portrait distance.

Sensor size matters as much as the aperture. A larger sensor needs a longer lens for the same framing, and the longer lens is what thins the plane, which is why phone footage looks deep even wide open.

Because the band is so thin, focus has to be placed on purpose. On a face it goes on the near eye. On an object it goes on the edge nearest the camera.

When to use it

Use it for close work on a face, for a detail that has to be lifted out of a busy background, and for any shot where the location is a liability.

Move off it when the audience needs the room. Shallow focus removes the geography, so a scene cut entirely this way leaves nobody sure where anyone is standing.

Told apart from its neighbours

Bokeh is what the out of focus part looks like, and shallow focus is the decision that produced it. You can have shallow focus with a plain grey wall behind and see almost no bokeh at all.

The test is whether there are point lights in the background. Bokeh needs them to render as discs. Shallow focus needs nothing but a wide aperture.

bokeh

On film

Hoyte van Hoytema shot Her (2013) close and long, so Joaquin Phoenix stays sharp inside a city that is mostly warm blur. The film spends almost all of its running time on one face with the world dissolved behind it.

Her (2013)

The prompt

Replace the blanks, keep the rest. Then run it on a video model.

shallow focus on <subject>, very thin plane of sharpness, everything nearer and farther falling soft, wide aperture

Run it

What goes wrong

The plane lands in the wrong place, usually on the ear or the shoulder. Name the one thing that must be sharp, which on a face is almost always the near eye.

The second failure is a background that is soft but still busy. Say the background is fully dissolved, or give it a simple tone to dissolve into.

Leave out

deep focus, small aperture

Watch for

Name the one thing that must be sharp. Usually it is the near eye.

Questions

Shallow focus keeps only a thin plane of the scene sharp, so everything nearer and further than the subject falls soft. It is produced by a wide aperture, a long lens, or a close camera.