[Yes] I bought one of these earlier this year. Quality construction both physically and optically. Resolution is very good indeed. Using a so so Canon lens (70-210 f/4), the image sharpness on my M5 is noticeably higher with the Metabones unit than without it. My EF 35mm f/2.0 IS with the Speed Booster becomes a sharp 40mm f/1.4 with IS!

[0.47 lb] I have used Metabones speedbosters for years now and have had nothing but a great experience. I own many Canon EF prime lenses from my days shooting event photography. In tandem with the Canon EF-M lens adapter, I can effectively get two focal lengths out of one lens. Bringing 1-2 lenses into the field and both of these adapters, I can effectively cover the full focal range that I would ever need in a much lighter kit.

Metabones products have a high build quality, very clear optics, and even a rubber gasket to help keep the elements out of your camera (pairs nicely with a weather sealed lens). When the need arises, I will buy more Metabones products without hesitation.

[Yes] I tested a 50/f1.4, 50/f1.2, 24-105/f4, 28-135/f3.5-5.6, 85/f1.8, 35/f2, 24-70/f2.8, 70-200/f2.8, and Tamron 150-600/f5-6.3. Autofocus works just was well on my M50 with the Speedbooster as the lenses did without it. Actually, most seem faster, maybe because the speedboosted image is brighter. AF, IS...you won't even know the speedbooster is there.

More lenses to test, but these I've tried so far functioned as advertised, were reasonably sharp to the corners, and most vignetting, distortion, and CA could be fixed by Adobe Camera RAW lens fix just as they could without the Speedbooster. ACR did not detect the underlying lens, but the actual lens could be selected and then ACR lens correction functioned properly.

Data reported to Adobe Bridge varied, with the usual being focal lengths shown as the actual x .71 (24-105 shows up as 17-74.). Max apertures were all one stop faster, and show up that way in the camera and in Bridge--except for the 50/1.2 which shows its original apertures (Metabones will not report apertures under 1.0 so as to avoid errors in cameras and software, so the 50/1.2, which would be f0.85 shows as 1.2.) The 50 1.4, and all lenses of F1.4 or slower, though is reported as 1 stop faster. All in all, the quality seems good enough and brings new utility some old lenses, and new ones too.

If you have a Canon mirrorless and a bunch of full frame EF lenses, this could be useful, and it's less expensive than Metabones' other Speedboosters. And really, haven't you always wanted a 50mm F1.0?

[1/4"-20 Female] This speedbooster works well with the lenses I want to use it with. Canon R7 with a few Sigma lenses. It yields great image quality with my 150-600 contemporary lens and gives me F3.5-F4.5. With the 1.6x crop thats still well over 600mm at F4.5. And over 1200mm shooting 4k crop mode on the R7. Its faster than the lens by itself at this focal length and image quality is still fantastic. Highly recommended for the R7 if you need more speed or even wider angle with your EF lenses on the R7.

[Canon EF-M] It’s an expensive piece of metal but it works really well and allows some character of lenses to shine on the Fuji. I’m less concerned with the field of view and more interested in adapting vintage lenses and what that brings to the system.

[Canon EF-M] Fantastic addon for my Komodo. Wanted a booster to play with my Mamiya 645's, and not disappointed at all. Perfect!

[Yes] Works incredible with our RED Komodo's. Love the locking mechanism. Autofocus still works perfectly.

[1/4"-20 Female] I was waiting for this to come since the release of the EOS R, and I just love it, yes it is not 1x but 1.2425x crop, but all my FF frame lenses and the Sigma 18-35mm work, with a little vignetting at 18mm but it works. 4K from native pixels instead of pixel binning or line skipping are sharper, and with FHD crop mode sampled from the 4K area, sharper and smaller files, can't recommend enough to all EOS R videographers.

[Canon EF-M] I needed a Bowens mount speedring for my Chimera softboxes and I wanted to avoid using adapters because that recessed the flash tube inside the bracket. Pretty thrilled this even exists and works perfectly for a low cost. I did ream out the holes a slight bit to let the rods slide in and out a bit easier but it's not a necessary step to take.

[Canon EF-M] I love both the concept and execution of the Metabones Speedbooster. It works as promised- great image quality while increasing the lens speed and FOV. Autofocus and stabilization translate flawlessly. EF-S lenses do not fully cover an APS-C sensor and are unusable with this adapter.

If you're on the fence about the Metabones vs Viltrox and other more affordable speed boosters, look into reviews. Yes, the less expensive versions work and boost as advertised, but the image quality you get from them- the fine details, contrast and color- all suffer from what I can tell.

My only small complaint is that the image seems to be more prone to light flares. They pop up at more angles and I believe they are a byproduct of the special optics in the adapter. Hopefully if they are unavoidable, you can work them into your shots or I'd suggest using your lens' hood. I would subtract a half star for this, but opted for the 5 since you cant rate by halves. Great product!!