It may be only in 1/1000 cases, does that make it useless to warn others to handle with caution? I don't care much for the damage other than reselling value if I ever want to sell the camera, others might more.

The Nikon G and the Pentax PKA versions have aperture control, it is mentioned in the first post. All the others you need to use lenses with manual aperture ring.

Thanks @haavard & @joethepro. It was a bit hard to see. I hope closing down one stop isn't too hard to manage, just in case; at least for use with ND filters.

Have any of you considered the 6.5mm 3.5 fisheye or the 8-16mm 4.5-5.6? I'm going for the 11-16mm as a low light wide-normal wide angle lens, though those other two seems like good lenses for ultra wide angles, though not fast enough. In my other topic, someone raised concerns of vignetting, but I don't see why an APS-C lens won't work fine with this adapter on m4/3.

From the research I recall, I couldn't find any mention or examples of it. One of the reasons I'm so interested too. I can't really imagine what they'd look like though, sounds like it'd give crazy results.

I've heard from someone that it's a stereoscopic fisheye, and I had no idea what the hell they meant by that as I had assumed that all fisheyes had been using one perspective. I think that might be one reason behind the 6.5, or it could be 8mm as several have argued :) Refer to http://en.wikipedia.org/wiki/Fisheye_lens#Mapping_function for those who've no idea what I meant.

@Vitaly, Is the RJ Manufacturer/builder open to some suggestions like light modifications on their adapters speedbooster ?

Also, do thew still offer the tripod mound ring ?

Thanks to answer

@Vitaly,

First suggestion: write apperture mesures/marks on the adapter so we can have more controls on the apperture wheel, especially if the lens used lacks one. See this for exemple: http://www.bhphotovideo.com/c/product/1002612-REG/metabones_mb_nfg_m43_bm1_nikon_g_mount_lens.html

About the mount ring, I was wondering if it was possible to get one without the adapter since the first time I bought the one for nikon mount I didn't think I would need one.

Other suggestions might follows, but I thing that gonna be all for now.

How do I know if it's the older adapter the one I have ?

Have there been any side-by-side comparisons between the different focal reducers? I'm especially interested in any image quality differences between this, and Metabones.

Also, do we know if they are working on anything stronger than 0.72x? Maybe something better suited for the GH4?

Ah! It took a while to get here. But in the end it was worth the wait. Own fault for wanting the free shipping (no import charges, yay!). Free shipping is not so quick. Easy peasy put together. Lens turns on smoothly; in turn the adapter attaches smoothly to the GH4 as well (maybe some added markings on the tripod collar and lens turbo would've been nice for easier alignment of the two in order to get the tripod base exactly level). So far, so good. Happy camper here. Thanks Vitaliy & RJ!

Now just gotta find some time for some vigorous testing. Unfortunately a couple of long days work ahead of me first.

Is there any reason stacking a dumb adapter on this would lower IQ?

Because adapters are not ideal things :-) But for video tasks if additional adapter is not faulty you are usually ok.

I've gotten the Nikon (F/G) to M43 one, because the newschool Tokina 11-16mm f/2.8 and Sigma ART 18-35mm f/1.8 give you a very nice ability to shoot wide and in somewhat lowlight conditions. Especially with the rather small crop sensor of the GH4/BMPCC, I find it really convenient to be able to use these lenses and use a focal reducer in combination with 'em. Pretty sure 'new' refers only to the addition of the adapter's collar / tripod mount. It's a rather nice addition though, certainly if you're working with some heavier/bigger glass.

Just got back from a trip to China (I took the FZ1000 with me to keep travelling light) and have some days off now to fully test the RJ Lens Turbo out (if weather permits to go out and shoot some).