I love this speed booster. It's basically a reverse Teleconverter. Instead of adding lens length and reducing light, this thing decreases lens length and increases light. Great for running older, cheaper, EF lenses on your RF camera.On a APS-C camera, the lens will effectively open up one stop and the lens length will become nearly the same as on a full frame camera.Just an awesome adapter.

Bought it from manufacturer, however could not leave a comment there (comment was deleted twice), so decided to write here.I have an R7 and everyone, who has this camera knows that a good enough camera still does not have good lenses, so you start thinking how to deal with it. It has very dark and short wide zoom, it has very dark and small superzoom and has no own affordable primes (some from Sigma overpriced arrived lately).So I wanted to try a speedbooster and since Canon not only blocks 3rd party lenses but also does not support adapters much, I had very few choice but Meike, especially given that their speedbooster is relatively new. I've tested it a lot and tested any possible lens with it so I know what I'm saying.1. optics is good. I've never found loss in quality. I wanted to get a compressed picture for even improved quality. That I did not find, but there is no decrease in picture quality either, except to, maybe, minor decrease in contrast. But it's not very apparent and usually appears under bright direct sun. Moreover, it does not have a purple spot in the center like the native Canon speedbooster, so optics wise it's even better. Cannot compare to Metabones, but given internet reviews of canon and viltrox speedboosters, optically this one is the best.2. The AF is awful. It does not work normally with most of the lenses. It worked kinda OK with Canon EF 40mm, always failed with Canon EF 50mm F1.4 (backfocus), and mostly fails with Canon EF 50mm F1.8 STM. Note: all these lenses AF worked ideally with the regular adapter with my Canon R7, so the problem is with the Meike. I also modified the 55-250 zoom lens to put it on this adapter and so far this is my only lens working properly with this speedbooster, although properly does not mean ideally: lens stabilization weakens (probably due to the lens itself), AF is slower (still OK) and there are some margins / vignetting - although if focused close enough, you get full coverage. I also have EF-S 10-22 and Tamron 200-500, but these do not have working AF so cannot tell, though EF-S 10-22 work starting from 12mm and has full coverage, so you can go wider than the 16mm FOV which is nice to have.3. The lens specifications are not as advertised. It is advertised as 0.71x, providing with 1 extra stop of light. All my testing showed that it is 0.75 and provides some 0.6 stop of light. Now, 0.75 might seem still good (viltrox is in reality 0.8, for example), but, it gives you ultimate crop 1.2 on Canon and 1.2 means that you still lose significant part of the image. Canon APS-C covers 40% of full frame sensor and respectively the lens, with this speedbooster you get 70% coverage instead of 77.5% coverage and it's still significant difference. Concerning light, you get almost 1 F-stop (0.94), but you get some 0.6-0.66 T-stop, given that there are 5 glass elements in the adapter and some loss of light is inevitable. This is almost normal, but only if is mentioned in the advertisement.When posting on Meike website, I was putting 4 stars, but since they kept deleting my comment, I'm putting 3, especially given that they have no intention to update the firmware. If firmware was updated to improve AF (let it be slow but accurate), than I would still put 5, since the crop factor difference is not huge, just a bit disappointing.

I do not understand, why the guy with the R50 is writing this what he says! I have also the R50 and it works like with the original Canon RF Speedbooster, You have at the beginning the message, that the firmware is not supported this hardware. When you press ok, all is working. Also with the Canon, Viltrox Speedbooster you have the same message, when you switch on the camera. but maybe he do not knows it. but look also youtube videos, also on original canon speedboosters and vitrox speedboosters you have this warning message, when turning on the camera.I tested also my EF-S to EF modded EF-S lenses from canon, wich have always problems with speedboosters, when they are not EF modded. When you are using the 10-18mm STM EF modded, you should start at 12 mm, because the glass is touching the glas of the lens. Also with the 18-55 stm you should start at 24 mm, because the same issue.with the Sigma 18-35 art lens, you have a vignietting at 18mm. you can crop a bit or you can start at 20 or 24 mm. then you do not see at least at 24 no vignietting anymore. Also other APS-C made lenses show vignietting, under 24 or 20mm. This is physically normal.all other fullframe lenses are working wonderfull. depend wich quality of lens you have, maybe you have some color fringing or cromatic abaration, when you shoot at high apature.but this you have also on metabones adapters, when you put cheap lenses on it.I have many speedboosters and this one from meike RF to EF is one of the best I have.Now you know, that it is also working perfect with the Canon R50. Also with modded EF-S lenses.With STM Lenses you have also the best autofocus performances. Maybe the Canon EF 24-105 STM would be the perfect and lightweight run and gun solution. This STM Lens do not need any EF-S to EF modd and it is also for fullframe.I choose the meike adapter over the viltrox adapter, because it is weathersealed at least in waterdrops and dust.with an R7 and a EF L series Lens you have a weather sealed setup.Wonderfull

Purtroppo la qualità del fotogramma decade irrimediabilmente perdendo il senso dell'acquisto.Sconsigliatissimo.

Worst speed booster I ever had. I own a canon R50 and I purchased it for my R50 and when I put it on I got a notice that it wasn’t compatible. So I figured it was a firmware issue so I went to my computer got onto there website and the firmware for this product doesn’t exist neither is the product on there website at all. So I tried contacting customer service from the website and there customer service rep was named “BRUCE LEE” lol and I got no help whatsoever. So I’m returning the same day I recieved it

The only caveat is the message you clear saying not compatible. Just click okay and it works great. Hoping there will be a software update someday to make it compatible. I do Motorsports photography and this never comes off on my camera. I use a Canon r10 with EF mount "L" lenses.

This 0.71x speedbooster has performed great in the few weeks that I've been using it. I've tested it on my EOS R10 with a variety of EF lenses from a EF-S 10-18, EF Sigma primes, and older Canon L lenses. I have had no issues with disconnection or autofocus. I ran it through a wedding using the R10 as a third body paired with a 70-200 2.8 and 85 1.4 and it worked flawlessly! The custom mode dial is great since the R10 doesn't have a rear scroll wheel, I can now use this as my exposure compensation dial. The increased light sensitivity worked great in low light reception situations along with off camera flash. So far a great adapter/speedbooster! Excellent alternative to the branded one and also great since a similar one is no longer available.

When it works, its the best thing EVER!Shooting EF Tamron G2 and Canon lenses on an r7 at indoor sportng events becomes joy🥰Almost better than full frame open apature, and focal lengths...Then she looses connection. It may only happen a few times a night, but that means i cant use it for weddings😪

I'd say overall I'm impressed with this little adapter. It will effectively make your full frame lenses true to their focal length and depth of field on super 35 R mount bodies. The custom programmable custom thumbwheel is a nice touch. It's fully firmware-updatable in that there's a USB C port in the adapter.What I don't get, and I did not run into any problems, is that they include shims for you to tune the adapter. I'm pretty sure Canon has zero deviation on all their focus plane distances, so I'm having a hard time understanding why you'd need to embrace the use of shims as an end user. If you do have an issue, you'll find yourself disassembling the adapter to add shims, checking, repeating if necessary.It seems like a lot of work kicked down the line, but at the same time, this thing is less than half of the Canon OEM version, so it becomes a time vs money thing.