Metabones T Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Micro Four Thirds-Mount Camera (MB_SPEF-M43-BT4) 4PC Accessory Kit

Like so many, I decided to painfully purchase this specifically for the adapt the Sigma 18-35mm lens to the Panasonic GH5("painful" because the price). I did a lot of research. especially between the Metabones XL(0.64x) vs the Ultra(0.71x), and the answer IF you plan to use get more Canon glass that is EF-S mount adaptable rather than EF, then this is the Speedbooster to choose assuming you don't want vignetting. I have not gotten to use the adapter much. I've only had one test day since I received it about 2 weeks ago. But, the test footage results with the Sigma+Ultra Speedbooster were outstanding. They were certainly as good as everyone else online made them out to be. I have not tested the adapter on any other lenses and probably will not as I got it specifically for the Sigma 18-35mm.A couple of things to note:I did a test video with my Panasonic 25mm prime lens the week before I did one with the Sigma 18-35. I DID see a difference. BUT it was not that crazy of a difference. I say this because the biggest downside to my new set up is the weight and bulkiness of the camera. The Metabones ain't light. The Sigma 18-35mm REALLY isn't light. Literally every Panasonic MFTs lens is. I personally like to hike with my camera. This is no longer an easy process if I want to bring the lens and adapter along. Think about that before purchasing.The video I saw of the Metabones Ultra plus Sigma lens stunned me. I was willing to shell out the money. While I haven't gotten the same results, mainly because I haven't had the time to play with it as much, I think the new setup will get better and better rather than worse and worse.I didn't like that the Metabones box didn't come wrapped in plastic. It made me wonder if it was second hand. Also, while the adapter locks in well, there is some odd friction between it and the camera body as well as it and the lens. It's like it rubs a little bit too much before locking in. Can't say I love that.The price hurts. $650 is just hard to pay for an adapter. I know it unlocks a whole new world of lenses to choose from but boy is that a lot to pay for a key. Especially because it's so small. I'd love to know the breakdown of costs to see how much Metabones is actually getting out of the deal. I also would love to see a legit competitor to maybe drive the price down a little.To all who are considering this purchase, don't forget that at the time of this review that Panasonic just released the news about their full-frame series they are launching soon. That will feature an L-Mount system making this adapter useless if you plan to upgrade... which I do. So, who knows. Maybe there will be a slew of used ones on the market soon being sold for those choosing to upgrade. Not gonna lie, I'll probably be one of those people.One last thing. I read a lot of stuff about the lacking in quality of the photos taken with the Metabones+Sigma lens. I didn't find that quality was poor at all. I thought they looked as sharp as all the other photos I've taken with other lenses. Maybe because I'm more video than photo I couldn't notice real differences, but I didn't think the results were bad.If you have the GH5, and you don't go the prime lens route, the Metabones - EF-S lens route is a good one.

The speed booster is awesome in lowlight fun production. It wiggles a little on the GH5S. I’ve been told this is normal but just a heads up for new buyers. Only owned for a couple weeks but will update if anything goes wrong

Very happy with my purchase of the .71 VS. the .64 version of the Speedbooster. See the Metabones website for differences. But basically,• Increase maximum aperture by 1 stop• Increase MTF of any lens attached• Makes lens 0.71x widerI have a Tokina 11-16 lens which when paired with the SB, is a great combo. Everyone raves about the Sigma 18-35, which will probably be my next purchase when I find a good used one.

Have used this item before when I attended University. It was great, so I had to buy one for myself!

It’s great but sometimes it’s slow at autofocus so it’s best to manually focus.

Magic magnifier for lenses. Especially helpful for use on the GH4 and other M4/3 cameras that don't perform well in low light.