Sound focus

Sound focus is a concept relevant to the presentation of 16mm films with optical soundtracks on projector models with sound focus controls.

Background

Frames from SMPTE's "Jiffy test" film showing the frames for subjectively assessing sound focus. On one side of the splice, the emulsion position is in the "A wind" position and on the other side of the splice it is in the "B wind" position.

16mm films (and other nonsymmetrical formats like 8mm and Super 8) vary in their emulsion orientations depending on the camera stock type and lab processes that produced them. Depending on the workflow that produced it, a reel you hold with the sprocket holes facing you might have its emulsion layer facing out (away from the hub of the reel) or in (toward the hub of the reel). These orientations are referred to in technical literature as "A wind" and "B wind." Both are common.

In a projection setting with normal 16mm threading (sprockets toward you and feed reel turning clockwise), "A wind" films are oriented so that the emulsion is toward the lamp and "B wind" films are oriented with the emulsion toward the screen.

Purpose and use of sound focus controls

Sound focus controls allow the sound lens in a 16mm projector's sound reader to be fully focused on the emulsion layer of the film regardless of "A wind" or "B wind" emulsion orientation. This allows optical soundtracks on 16mm prints to be played back sounding their best.

When sound focus is set correctly, a little more surface noise will be audible but the soundtrack will sound brighter overall. When sound focus is set incorrectly, there will be a loss of high frequencies and the sound will be muddier.

By design, sound focus settings are meant to be binary, corresponding to "A wind" and "B wind" emulsion orientations. However, sound focus controls on projectors often allow for gradual adjustments. This enables the use of sound focus controls to compensate for other optical sound issues, like optical soundtracks with lots of hiss.

What if my projector doesn't have sound focus controls?

Many common projector models do not have sound focus controls at all. These projectors are designed to split the difference between "A wind" and "B wind" orientation. If you're using a projector that lacks sound focus controls, you don't need to do anything special.

16mm projectors with sound focus controls

Sound focus controls are present on some but not all 16mm projectors. Models with sound focus controls are listed below. If you aren't sure whether your projector has sound focus controls, consult your manual.

Terminology for sound focus and sound focus options varies between manufacturers.

• All Eastman models (the options are labeled "F" and "R" on the projector and the manual refers to "sound focus")
• Some Kodak Pageant models (where it's called "sound focus" or "sound optics focus" or sometimes as a "fidelity adjustment")
• Kinoton/Norelco FP16 and FP18 models (where the settings are referred to as "standard" and "nonstandard")
• Norelco EL series