@CFreak - I know that officially the GH4 is not supported on the BMCC Speedboosters, but there are lots of examples of people using them anyway... even Philip Bloom has talked about this. But it does sound like maybe the electronics are not compatible for use with autofocus? Maybe just aperture control? What about image stabilization?

afaik, you cannot adapt aspc lenses to m/43 using the metabones speedbooster

@psyco - thanks for the reply/info! I think the important thing is that the focal length measurements of the Rokinon lenses aren't approximations but the actual focal lengths of the lenses and that no matter the rear element/mount I simply calculate the focal reduction and then the crop as normally to find out my 35mm-equiv viewing angle. whether or not i see vignetting is just a function of the crop on the rear element. so there's no difference in adapting a Rokinon lens that has full frame coverage vs ASP-C (as long as I'm using GH4 in C4K).

Has anyone shot resolution charts with and without the speedbooster?

the native projection coverage of the lens needs to be larger.

@Wichtelfieber The image cirlce of the EF-S lenses equals the imaging circle of the Nikon DX lenses, especially true of third party manufacturers of lenses for these mounts; and the Nikon DX lenses work just fine on a speed booster. My question isn't regarding the image circle, but rather the electronic connectivity of the Canon adapters.

@Jive, that's great new then. If third party lenses have an EF mount and not an EF-S, then it ought to be mountable on the speedbooster simply because it's the same mount. I've looked at my EF-S lenses (Canon lenses) and they all have that protrusion, by there's a space between the it and the glass element; basically nothing. So I would guess that third party lenses should work just fine on either adapter, given the mount. That link you gave says that as well. Great news, man. Thanks :D

I wonder why this isn't mentioned too often. I had thought I was stuck to Nikon speedboosters & without electronic integration if I were to use any third parrty lenses :) 16-300mm Tamron ought to be a beast.

http://www.thephoblographer.com/2015/02/26/first-impressions-zeiss-35mm-f2-loxia-sony-full-frame-e-mount/

I got the Metabone Canon EF Lens to Micro Four Thirds Speed Booster which i wish to pair with my next purchase, Sigma 18-35 1.8 lens onto my GH2

Will the GH2 or will it Not need an external power source via MicroUSB to activate the Speedbooster functions of 0.71x reduction and 1 stop lesser.

If the answer is yes, could anyone who has experience share a tried and tested third party 5 volt MicroUSB power supply brand i would need to buy for the same?

This from Metabones...

scroll down , the comparison between the 2 different models is listed :)

http://www.metabones.com/products/details/MB_SPEF-m43-BM1

"I got the Metabone Canon EF Lens to Micro Four Thirds Speed Booster which i wish to pair with my next purchase, Sigma 18-35 1.8 lens onto my GH2

Will the GH2 or will it Not need an external power source via MicroUSB to activate the Speedbooster functions of 0.71x reduction and 1 stop lesser.

If the answer is yes, could anyone who has experience share a tried and tested third party 5 volt MicroUSB power supply brand i would need to buy for the same?"

The 0.71x reduction and 1 stop speed increase are done by the optics, and no power is needed.

Power is needed to control the iris and activate image stabilization on EF mount lenses. The GH2 has an active m43 lens mount, so it should work fine with your Speed Booster, meaning you can control the aperture of EF lenses from the camera. External power is only needed for the special 0.64x BMCC - EF version because the BMCC has a "dead" mount with no electronic connections.

@club_irate:

Your calculation is right (about the focal length).

About vignetting: Well - I cannot answer your vignetting question (as I only used the Sigma on a GH4 in 2.3x crop and 2.0x crop til now) - BUT: Why do you want to go for the SpeedBooster if you´re using the GH2 with the WAY lower crop factor (compared to the GH4 4k mode especially)?

For example: You could also get a normal EF to MFT active adapter without a reducer glass element. (Like the Aputure DEC or the new upcoming / now available Kipon EF/EF-S to MFT adapter - Which is also delivering nice AF performance. At least according the first sample videos.) The HUGE pro of that solution would be, that you get a way better usable focal range on the GH2 (around 35-65mm full frame equivalent - All still on the original F1.8 aperture of the lens which is also quite fast aka "fast enough"). AND you´re also saving money (as the Metabones EF SpeedBooster is quite pricey around 600$ - The new Kipon is actually around 300$ which is WAY more attractive price wise). You could even go for a used (or new) Samyang / Rokinon 12mm F2.0 native Micro 4/3 lens instead (for the money you saved NOT getting the SpeedBooster) - That would be nice, as the 12mm F2.0 is WAY handier on glidecams, gimbals, shoulder rigs and so on (as it´s WAY smaller and lighter).

AND with that choice you would get an even wider focal length range (for STILL a lower price if you buy the 12mm lens used ^^) - The 12mm would give you an additional ~22mm full frame equivalent focal length. Btw.: You can still buy a SpeedBooster in the future (if you want to use the Sigma 18-35mm F1.8 on a GH4 for example as an "always on"). With the booster on the GH4 (2.3x 4K crop) you would get the quite similar 30-57mm (compared to the 18-35mm F1.8 with the standard adapter on the GH2 which is giving you 35-65mm). Btw.: You can go even cheaper if you don´t want the autofocus feature AND if you don´t want to use EF lenses on the adapter - As for the Nikon lenses Metabones is also offering a very nice controllable passive adapter (also without a reducer glass installed - But it comes with the same (better) aperture control mechanism like on the SpeedBoosters):

http://metabones.com/products/details/MB_NFG-m43-BM1

Just keep in mind: With that adapter you cannot achieve image stabilization with lenses (as it´s a passive adapter). AND you also don´t get AF in ANY kind. So if you plan to use existing EF lenses, I would go for the Kipon EF adapter (or any other solution).

I hope I didn´t confuse you further ^^.

LG

Petersburg, VA, USA, Jun 05, 2015: Caldwell Photographic Inc. and Metabones® are pleased to announce the Speed Booster XL 0.64x, a new Micro-4/3 mount Speed Booster® adapter designed exclusively for the Panasonic GH4 and other selected Micro Four Thirds cameras, with a magnification of 0.64x. The Speed Booster XL 0.64x uses an advanced 6-element optical design to achieve extraordinary optical performance at apertures up to an incredible f/0.80, a new record for Micro Four Thirds format.

The new Speed Booster XL 0.64x reduces the full-frame crop factor of the Panasonic GH4 from 2.0x to 1.28x, thus effectively transforming these cameras into APS-H format. When the GH4 is used in Cinema 4k video mode the horizontal full frame crop factor is reduced from 2.34x to 1.50x, thus effectively transforming the GH4 into a super-35 format 4k cine camera. In addition, the speed of any attached lens is increased by 1.3 stops, with a maximum output aperture of f/0.80 when an f/1.2 lens is used. For example, a 50mm f/1.2 becomes a 32mm f/0.80, which is the fastest aperture available for full size Micro Four Thirds format.