Depth of Field Test

Before shooting a critical close-up or working with a very wide aperture, the focus puller performs a depth of field test. This is not a gimmick – it's about knowing the exact zone where focus lies when focal length, aperture, and distance are fixed. At f/1.4 at 50mm, this zone can be as little as 10 centimeters. Anyone who hasn't measured this beforehand is shooting blind.

The workflow is practical: The focus puller positions themselves with a measuring tape or measuring board at eye level with the camera. They measure the planned focus plane – usually the actor's eyes – and note the distance. Then, the camera is focused to exactly this distance, usually with a follow focus or by hand. Now comes the test shot: you roll for a short moment, moving slightly forward and backward to see where the focus begins and ends. The footage is immediately checked in the video village or on a small monitor. Some DoPs shoot in parallel with a smartphone or tablet – quick & dirty, but effective. The measurements and findings then go into the puller's focus notebook: "f/2.8, 2.5 meters = focus from 2.2 to 2.8 meters." This way, they know how much leeway the actor has.

This becomes particularly critical with very long focal lengths (teles) or extreme wide apertures – there, the depth of field shrinks to millimeters. With a 200mm lens at f/2, it's possible that only the tip of the nose is sharp. The test is also essential for extreme close-ups, such as macro work on an eye or objects. Some scenes require multiple tests with different positions or aperture values to advise the DoP and director whether the planned shot is even feasible.

The test saves you stress later: no focus errors in take 7, no discussions at the editing table about why the eyes are out of focus. It's craftsmanship – calm, methodical, professional. A good puller sees the test as part of their preparation, not a delay.