Blackmagic Design Camera Lens Cap B4

Blackmagic Design Camera Lens Cap B4

The Blackmagic Design Camera Lens Cap B4 is a specialized Body Cap designed specifically for the 2/3" B4 broadcast mount. This cap is a critical accessory for operators using the URSA Broadcast G2 or the original URSA Broadcast, as well as any URSA Mini Pro fitted with the optional B4 mount adapter.

Purpose and Protection

The B4 mount is a staple of the ENG (Electronic News Gathering) and sports broadcast world. Because this mount system often involves a complex optical block and specialized electronic connectors, keeping it sealed is paramount.

• Optical Path Security: The B4 mount on Blackmagic cameras usually sits in front of a specialized glass corrective element (the optical block that compensates for the prism used in 3-chip B4 lenses). This cap prevents dust and smudges from reaching that critical glass.

• Electronic Pin Safety: It protects the 12-pin Hirose-style communication pins or the internal mount contacts that provide power and iris/zoom control to professional broadcast lenses.

• Mechanical Integrity: It shields the triple-lug bayonet system of the B4 mount from nicks and debris that could interfere with the smooth "twist-to-lock" action of a broadcast lens.

Design and Build

• Material: High-durability, industrial-grade matte black plastic.

• Standard B4 Bayonet: Precision-molded to match the standard 2/3" broadcast specification. It utilizes the three-flange locking system characteristic of B4 mounts.

• Internal Clearance: The cap is hollowed out with specific tolerances to ensure it never makes contact with the corrective optics or the sensor housing, even if subjected to pressure during transport.

Compatibility

This body cap is the dedicated replacement for:

• Blackmagic URSA Broadcast / URSA Broadcast G2

• Blackmagic URSA Mini Pro (4.6K / G2 / 12K) when the optional B4 Mount Kit is installed.

• Blackmagic Studio Camera 4K Pro / 6K Pro (when adapted for B4 lenses).

Operational Insight

In the world of live broadcast, cameras are often moved from cold trucks to humid stadiums or dusty sidelines. The B4 body cap is your first line of defense against condensation and fungal growth on the internal optics.

Unlike EF or MFT caps that "click" into a locking pin, a B4 cap is held in place by the camera's rotating locking ring. To install it, you line up the three tabs, insert the cap, and rotate the camera's outer ring. This creates a highly robust mechanical seal that is much harder to "knock off" than a standard consumer lens cap.

Pro Tip: If you are a rental house or a news station, these caps are essential "bin items." Because B4 lenses are often massive and heavy, they are frequently stored separately from the camera bodies during transport. Never ship a B4-mount camera without this cap securely locked in place to prevent the mounting ring from vibrating loose.