The “Z CAM Interchangeable Lens Mount with Active Lock for Z CAM E2-M4 (MFT Mount)”, to give it its full title, is the world’s first positive-locking MFT mount. It fits on any of Z Cam’s flagship series cameras, though it’s primarily intended for the E2-M4 with its 4/3” sensor.

The Problem

Bayonet mounts are common in still cameras. Lenses mount with a twist, rotating the lens’s mounting flanges behind similar flanges on the camera body. Flat springs on the body flanges snug the lens up against the body, while a locking pin secures the lens in place.

Bayonet mounts are easy to work with, but their spring-loaded nature means that the lens can rock or wobble in place, especially if the lens is heavy or if a fast focus pull is performed with a stiff lens. These movements aren’t normally visible when a camera is taking still photos, but with a motion-picture camera hard-mounted on a tripod these bobbles can easily show up in the picture. 

A separate lens support can minimize or eliminate the movement, but that’s something else that has to be dealt with, and it’s just morally wrong to have use such a support for a lightweight prime!

The Z Cam E2-M4 is supplied with a standard, bayonet-type MFT mount. it works perfectly well, but — as with any bayonet mount — there’s a little bit of play:

When using a follow-focus on a cine lens, a fast crank of the knob can rock the lens up or down slightly, and this shows up in the moving image. It’s annoying.

The Solution

A positive-locking mount (technically a breech-lock mount) prevents that problem by replacing squishy springs with a much more rigid clamping action. A cam action in the mount’s rotating collar causes the collar to grip the lens flanges ever more firmly as it’s rotated, positively locking the lens in place.

PL mounts are positive-locking mounts (that’s where the PL name comes from), and positive-locking EF mounts can be found on some Canon cine cameras, Panasonic EF-mount Varicams, and some Metabones adapters. Z Cam’s “active lock” MFT mount is the first (and, so far, only) positive-locking mount for MFT lenses.

The $99 mount comes nicely boxed, embedded in a rubber holder and capped with a body cap. There’s bag of four 2mm mounting bolts, and a spiffy 2mm hex driver (not shown in the photo):

With the mounts removed, you can see the dual rows of pogo pins the camera uses to talk to the mount; the mount in turn talks to electronic lenses for aperture and focus control.

On the back side of the stock MFT mount, there’s a dust gasket, and contacts for the pogo pins. The hardware at 9 o’clock is the locking pin for the bayonet mount and its pushbutton. The active-lock mount looks much the same, minus the locking pin hardware.

Here’s the mount on the camera:

And here it is with a Veydra Mini Prime fitted:

The difference is like night and day. With the stock bayonet mount, lenses attach as well as they do on any normal camera. There’s nothing wrong with that, but the lens can move around a tiny bit. With the positive-lock mount, the lens snugs down tight and becomes one with the camera, as if it was welded to it. There’s no play, no wobble, no flexing; I can pull focus as abruptly as I want, and the lens stays solidly in place.

What about flange depth? Z Cam says no shimming is necessary when mounts are swapped, and my Veydras, calibrated on GH4s and GH5s, hit their marks exactly when mounted on the E2-M4.

With the active lock mount, it’s like having a real cinema camera. I highly recommend it.

Any Drawbacks? 

The clear area at the base of the mount is about 58mm in diameter. Most lenses fit easily within that area, but those with especially broad bases may not. All my stock Panasonic, Olympus, and Veydra lenses work without a problem, but my Ukranian rehoused Zenitar 50mm f/2 tilt lens is too fat to fit. 

I’ve seen reports that some mount adapters are also too large. so you’ll want to retain the bayonet MFT mount for using those lenses or adapters. The mounts are easy to swap.

Pros

• Mounts your lens rigidly in place, the way a lens should be mounted
• Swaps quickly with other Z Cam mounts
• Carries lens data and control signals for aperture control, AF (when using electronic lenses)
• $99 cheap, like all Z Cam interchangeable mounts (other than the relay-lens mount)

Cons

• Lenses / adapters wider than 58mm at their base won’t fit.

Bottom Line

• If you use MFT glass on your Z Cam, especially cine glass with focus gearing, get this mount and be happy.

Disclosure: I purchased a Z Cam E2-M4 and an active lock MFT mount at regular retail prices. Other than that there is no material relationship between me and Z Cam, and neither Z Cam nor anyone else has offered me any discounts, bribes, free trips to Pismo Beach, or other compensation for this review.