Create a focal length constraint

A focal length constraint is useful for controlling the angle of view in your scene.

Determine focal length settings

The focal length settings are on the Solve Camera control panel. To help determine how to set these parameters, start by answering the following questions.

What is known about the focal length value?

Unknown value (e.g., video shot): Set the constraint type to Unconstrained and leave the value blank.
Known value: Set the constraint type to Fixed and enter the value. Create an animated attribute if the focal length varies.
Estimated value: Set the constraint type to Constrained, enter the value, and enter a variance. Create animated attributes if the focal length varies.

Does the focal length zoom or remain static?

Zoom: Uncheck the Static checkbox, which indicates the value is animated.
No zoom (static): Check the Static checkbox, which indicates there is no animation to this value.

Example focal length settings

The following table offers examples of how to set up focal length:

Shot	Focal Length	Focal Length Constraint Settings	Maya Live Result
Film with prime lens	Known constant value	Type: Fixed Value: lens setting (e.g., 32) Static: checked Variance: N/A	Maya uses your fixed focal length and keeps it constant.
Film with prime lens	Estimated constant value	Type: Constrained Value: lens setting (e.g., 32) Static: checked Variance: estimated buffer (e.g., 1)	Maya uses your focal length within your variance and keeps it constant.
Video with zoom	Unknown and varying	Type: Unconstrained Value: N/A Static: not checked Variance: N/A	Maya determines focal length and it may vary through the shot.
Video with no zoom	Unknown and constant	Type: Unconstrained Value: N/A Static: checked Variance: N/A	Maya determines focal length and it stays constant.
Film with manual zoom	Estimated value and varying	Type: Constrained Value: create an animated attribute Static: not checked Variance: estimated buffer (e.g., 5)	Maya uses your animated values for the focal length within your variance.
Film with motion-controlled zoom	Known value and varying	Type: Fixed Value: create an animated attribute Static: not checked Variance: N/A	Maya uses your animated values for the focal length.