KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH
The KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH property retrieves focal length information for a camera.
Usage Summary Table
| Get | Set | Target | Property descriptor type | Property value type |
|---|---|---|---|---|
| Yes | No | Filter or node | KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH_S or KSPROPERTY_CAMERACONTROL_NODE_FOCAL_LENGTH_S | LONG |
The property value (operation data) is a LONG that specifies a camera's focal length.
Remarks
You can use this property request to interpret zoom values. The range of zoom should be between lObjectiveFocalLengthMin/lOcularFocalLength and lObjectiveFocalLengthMax/lOcularFocalLength. (lOcularFocalLength, lObjectiveFocalLengthMin, and lObjectiveFocalLengthMax are members of the KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH_S and KSPROPERTY_CAMERACONTROL_NODE_FOCAL_LENGTH_S structures.)
For example, if lObjectiveFocalLengthMax = 105 and lOcularFocalLength = 35, then this camera is capable of a maximum optical zoom ratio of 105/35, or 3.
Also see the Optical Zoom section of the USB Video Class Device Class specification. This specification is available at the USB Implementers Forum website.
Requirements
| Header | Ksmedia.h (include Ksmedia.h) |
See also
KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH_S