KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH

The KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH property retrieves focal length information for a camera.

Usage Summary Table

GetSetTargetProperty Descriptor TypeProperty 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

Version

Available for Windows Vista and later versions of the Windows operating system.

Header

Ksmedia.h (include Ksmedia.h)

See also

KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH_S
KSPROPERTY_CAMERACONTROL_NODE_FOCAL_LENGTH_S
KSPROPERTY_CAMERACONTROL_ZOOM
KSPROPERTY_CAMERACONTROL_ZOOM_RELATIVE

 

 

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