ksproperty-cameracontrol-focal-length.md

title	description	keywords	topic_type	ms.topic	api_name	api_location	api_type	ms.date
KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH	The KSPROPERTY\_CAMERACONTROL\_FOCAL\_LENGTH property retrieves focal length information for a camera.	KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH Streaming Media Devices	apiref	reference	KSPROPERTY_CAMERACONTROL_FOCAL_LENGTH	Ksmedia.h	HeaderDef	06/18/2020

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

KSPROPERTY_CAMERACONTROL_NODE_FOCAL_LENGTH_S

KSPROPERTY_CAMERACONTROL_ZOOM

KSPROPERTY_CAMERACONTROL_ZOOM_RELATIVE