After using the Zhongyi Lens Turbo II for a while, there are some quirks and restrictions popping up. The optics of the Lens Turbo (LT) are very good and the mechanics look solid, too. But not all lenses are compatible and mounting the LT on the camera can be a bit fiddly – it’s always tricky to get it to lock. In contrast to a native lenses, the distinct “click”-noise when mounting is missing as you don’t turn the whole adapter, but only the locking flange. In any case, the adapter would still rotate easily when mounted. As it turns out, there is a reason for that…
There’s some lenses, which can not be properly mounted on the Lens Turbo because the aperture pin is blocked and others, where the rear lens element can collide with the LT optics. Hillyard Photography is maintaining a list of over 80 lenses with various mounts, which have been tested for compatibility with the LT II. There is also an active Flickr dicussion related to this list, where new findings are usually published first.
In case of the LT II for Minolta MC/MD, lenses where the back element protrudes more than 3 mm from the back of the mount when focused to infinity can collide with the Lens Turbo optics and shouldn’t be used. If you can mount the lens, but the aperture is stuck open or you can not fully mount it but the glass does not collide, you can most likely fix the problem by filing down the aperture pin of your lens by approx. 1 mm. Although I don’t like the idea of tampering with my lenses in this way, it’s a viable solution and does not impede the functionality of the lens. If you do this, just be careful with the metal shavings and make sure the lens is completely clean of them before mounting it on your camera. The shavings may otherwise lead to shorts or mechanical damage. This is especially important on cameras offering in-body image stabilization (IBIS) like the A7II, which use very fine electromagnetic solenoids to position the sensor that will magically attract all metal flying around in the mount.
If you are having problems focusing to infinity even with your compatible lenses, there might be an issue with the optical assembly in your Lens Turbo. Luckily, one adventurous user took apart his LT and documented how to adjust infinity focus. In short: You can screw the whole optic assembly in or out after removing the three screws on the back and loosening some glued parts. Have a look at the thread linked above for detailed instructions.
Mounting / Locking problem
As mentioned, the Lens Turbo has a very nice mechanical construction, but mounting it on the camera does not give you the same feedback when locking as mounting a native lens does. And it always tended to rotate while mounting or dismounting lenses. I originally thought the chamfering of the bore for the locking pin (see image on the left) was responsible and that the pin would just be pushed in inadvertently. As it turns out, that was not the reason.
Looking at the mounted LT on the A6000 of a friend showed, that the tab on the LT protecting the lens release button did not only protect it from accidental actuation, but also slightly pressed it down all the time. This resulted in the locking pin being slightly retracted when the LT was mounted on camera, which, in turn, made it very easy to just turn the Turbo (and scratch the plasic inside the mount) although the lock was seemingly “engaged”.
It can be argued, whether it was a design choice of the manufacturer not to rely on the locking system. In my opinion, this is a bit of a half-baked solution. A friend of mine agreed and decided to modify his LT accordingly. He used a file to shave off about 0.5 mm from the backside of the tab protecting the lens release button (see images on the right). The result looks nicely machined and had the desired effect: The Lens Turbo now mounts with the locking pin fully engaging and doesn’t twist easily anymore while mounting lenses. If you don’t fit the Turbo perfectly while mounting it to the camera and have to twist slightly to align it, the satisfactory “click” noise will be more pronounced, too.
All in all, this turned out to be an easy fix and really improves the confidence in the locking mechanism while working with the LT.