Fixing Chinese Focal Reducer to fit on BMPCC

I bought a focal reducer to use with my Nikon 24mm 2.8D on my Blackmagic Pocket Cinema camera.  Getting an effective 0.7 * 24mm, or 17mm starting at 1.8 (1 stop reduction) intrigued me. Andrew Reid, the genius behind EOSHD, is a big proponent focal reducers.  As a hobbyist, I couldn’t justify the cost of a Metabones adapter.  So I bought a Chinese knock-off on Ebay from C. Kee for $96, shipping included.  It was shipped within 24 hours and arrived exactly one week later.  Off to a good start!

Unfortunately, it would only turn a few millimeters onto the BMPCC, just enough to mount, if I handled it very gingerly.   If I forgot about it for a second, the lens would go crashing to the ground.  Anyway, I had promised Andy Lee, an expert on lenses and the Panasonic g6, who gives great advice on the EOSHD forums, that I would shoot some test footage.  First I shot Focal Reducer on BMPCC then Focal Reducer on Panasonic GF3 (which the adapter fit on perfectly).  He approved and said he was going to order one (he shoots Panasonic so wasn’t worried about fitting it to a BMPCC).

Then richg101 on the forum talked about taking it apart and checking the lens distance into the body.  When I did that I realized I could take the whole thing apart.  I studied it some more and the best I could figure is the flange on the adapter was getting stuck on the mount-flange.

Here is what the adapter looks like, looking at the MFT mount side.  Obviously, the adapter didn’t look like this when it arrived.  I had sanded it a bit trying to get it to fit.

Here’s another view.  If you look closely, you can see three flanges that twist under the mount flanges (which have springs underneath).  When the lens turns far enough a small bolt on the camera inserts into the adapter and locks it into place.


Here you can see a flange in profile.

In the BMPCC you can see there is a slight ridge/block that probably holds the spring into place.  I believe the adapter flange hits against this, ever so slightly.

First I take off the Nikon mount of the adapter.  There are 3 little screws.

After unscrewing a small locking screw,  I screw the lens out

Here are the three parts to the adapter.

And now I sand the inside of the adapter flanges down a bit.  I did a little, tested, until it fully locked into the camera.

Some advice.  Wear glasses.  You don’t want grit in your eye.  Eye doctors are expensive.  Also, make sure you wash/blow all grit away from the adapter before mounting it on the camera.  The smallest particle can show up on your sensor.

I may have ended up with a “bad” copy of a BMPCC mount or adapter.   These adapters don’t have names, so it is hard to see who is buying what on Ebay and Amazon, etc.  I’ve read reviews of what looks like the exact same adapter working on someone else’s BMPCC.   The good news is that all is not lost if you experience the same problem I had.  I hope you don’t though!

Now that I have it working, I ordered a Zenit 16mm.  With the adpater, I’d have 0.7 x 16 = 11mm time the 2.8 crop of the BMPCC, or 32mm.  Test footage to follow later!

UPDATE: even though I thought I cleaned it well, dust will come off it when screwing it onto mounts so clean really well, or get some really fine paper and get a blower to blow around the camera mount after you take it off.