Blackmagic Design URSA Mini Pro B4 Mount

Blackmagic Design URSA Mini Pro B4 Mount

The Blackmagic Design URSA Mini Pro B4 Mount is a precision optical adapter and mechanical mount that allows the use of standard 2/3" HD broadcast lenses on the URSA Mini Pro (4.6K, G2, or 12K).

While these cameras feature a large Super 35 sensor, this mount includes high-quality corrective optics that expand the light from a B4 broadcast lens to cover a specific "window" of the larger sensor. This preserves the lens's original focal length and prevents the optical degradation—specifically spherical aberration—that typically occurs when using a 3-sensor lens on a single-sensor camera.

Core Functionality

• Optical Correction: B4 lenses were originally designed for 3-chip cameras with a prism. This mount features integrated glass elements that correct for the optical shift, ensuring the image is sharp and clear across the entire frame.

• 1.1x Magnification: The mount provides a subtle magnification to ensure the B4 image circle properly covers the sensor's windowed area (typically Super 16mm, 2K, or HD window modes).

• Broadcast Integration: When paired with the 12-pin Hirose connector on the URSA Mini Pro body, this mount enables full electronic control of the lens:

  • Powering the Servo: No external cables are needed to power the lens zoom rocker.

  • Iris/Zoom Control: Adjust aperture and zoom via the camera’s controls, a remote ATEM switcher, or external Focus/Zoom demands.

  • Record Start/Stop: Trigger internal recording via the physical button on the B4 lens handle.

Professional Build & Design

• Bayonet Style Locking Ring: Features the standard broadcast "breech-lock" mechanism, providing a secure, rigid connection for heavy ENG zoom lenses.

• User-Interchangeable: Much like the EF and PL mounts, this is a 4-screw system that can be swapped by the operator in the field.

• Shim Adjustable: Includes a dedicated Shim Kit, allowing you to fine-tune the flange focal distance to ensure your lens remains "parfocal" (stays in focus while zooming).

Technical Specifications

What’s Included in the Box?

• 1 x Blackmagic URSA Mini Pro B4 Mount

• 1 x Moulded Mount Case (for storing your unused PL or EF mount)

• 1 x Turret Dust Cap

• 1 x Lens Rear Protective Cover

• 1 x Shim Set

• 1 x Set of Spare Mounting Screws

Operational Insight (2026)

In 2026, the B4 Mount remains a "secret weapon" for broadcasters. It allows you to utilize $20,000+ broadcast zoom lenses you may already own, providing a massive focal range (e.g., 22x or 40x zoom) that is nearly impossible to achieve with cinema glass.

Important Compatibility Note: While the mount fits the URSA Mini Pro 12K, you must use the 6K Super 16 or 4K Super 16 sensor window modes to match the image circle. Using the full 12K sensor area with this mount will result in heavy vignetting.