I'm using Viltrox EF-M2 adapter for a year already and I like it. It has compatibility issues, but when it works, it works great. With this test I wanted to show you just how good Viltrox adapter works with certain lenses and bodies, and what compatibility issues look like. Hence the video aimed primarily at testing AF speed and accuracy, all lens set to 17mm. Equipment: - three generations of Olympus cameras, E-P5 (TruePic 6 processor), E-M1 (TruePic 7) and E-M10.3 (latest TruePic 8) - native mZD 17/1.8 lens - Canon EF 16-35/2.8 L II USM, EF 24-105/4.0 L IS USM, EF-S 10-18/4.5-5.6 IS STM - Sigma 18-35/1.8 DC HSM Art - Viltrox EF-M2 speedbooster with latest ver.3.2 firmware and Viltrox EF-M1 plain adapter for EF-S 10-18 lens Summary: 1. mZD 17/1.8 is the quickest to focus at 0.14-0.15 sec on average. That was expected. What I did not expect, though, was the fact that all three generations of Olympus cameras AF this lens with the same speed. Strange, I thought Olympus improved S-AF speed in latest generation cameras equipped with TruePic 8 processor. My test shows otherwise. mZD 17/1.8 is also the loudest to AF in my test. This is probably due to aperture closing for framing and quickly opening for AF, but the sound is just too loud. 2. Canon EF-S 10-18/4.5-5.6 IS STM was a pleasant surprise. I tested it on plain Viltrox EF-M1 adapter since I could not modify this lens for speedbooster. The lens worked fine on all three Olympus cameras. It was very quick on E-M1 and E-M10.3 taking 0.23-0.24 sec to focus on average. E-P5 AF was OK at 0.34. AF accuracy was excellent which it should be at f/5.4 The best part of AF was the sound, or rather lack of any sound during AF. STM motor was a very pleasant surprise. 3. Canon EF 16-35/2.8 L II USM worked fine only with old E-P5. Despite only CDAF, E-P5 was able to AF this lens taking only 0.17 sec on average. Excellent speed! AF accuracy was also good. E-M1 was somewhat slow to focus this lens at avg. 0.37 sec. Worse still, it sometimes hunted for focus for 1 - 1.5 seconds. AF was accurate. E-M10.3 performance with this lens is a mixed bag. On one hand, AF is very quick and accurate for near objects. On the other hand, AF failed to lock focus on distant targets, trying to hit well beyond infinity mark. I would use this combo indoors, probably, but for distant objects you are left with manual focus only. 4. I had high hopes for Canon EF 24-105/4.0 L IS USM. I like this lens build without too much bulk, sharpness and constant aperture. It might be a good walkaround lens with speedbooster, but alas it has severe compatibility issues. AF speed is reasonable with near objects at 0.25-0.33 sec. But AF with distant targets is unavailable. Only E-M1 was able to lock focus on distant object, but it did so with apparent front-focus. 5. Sigma 18-35/1.8 DC HSM Art performed very well with E-P5, taking only 0.22 sec on average to lock focus. It is very good considering the large f/1.2 aperture of the lens on speedbooster. AF accuracy is excellent. E-M1 was slow to AF this lens at 0.43 sec. AF accuracy is good. E-M10.3 was even quicker than E-P5 to AF the lens. But E-M10.3 struggled to lock focus on distant target. It allowed to make a shot of distant object but with slight AF overshooting to backfocus. Sigma 18-35/1.8 focuses with loud metallic clicks. Strange for an ultrasonic piezo drive focus motor. AF noise probably renders this lens AF unusable for video with on-camera mic. Overall, Viltrox adapter has its compatibility issues. It is usable with those issues, though. And when it works well, like E-P5 + Sigma 18-35, it is a genuine pleasure to use.