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Question: how is the auto focus using l lenses to take videos
Document: Good idea and concept, but its hard to judge this product when using it on the EOS-M with its horrible focus. You don't really lose any stops with you EF lenses. The IS does not seem to transfer over. The EF lenses do what they are told, but a continuous auto focus and generally undeveloped Hybrid APS-C sensor is not fluently compatible with the current EF-s and EF lenses. Video is horrible with the CON AF on. It. 's just not pretty.
The adapter works as claimed. I've tried it with some Canon lenses I already owned, and the focus is both accurate and reasonably quick.The downside is that the adapter itself adds to the weight and length of any lens attached to it. In many instances this would discourage its use, because it would be difficult to hold it steady. And obviously it could not longer make any pretense toward &#34;pocketability&#34; or unobtrusiveness.
The camera has it's flaws. Believe what you read about it's failings in low light - not wanting to focus. So the only reason to buy the EOS M in my view is to use your existing Canon glass with a mirror-less lens camera. This adaptor makes that possible. It works flawlessly with all of my OEM and after market lenses. I can see the EOS M working for me when I am out in the field backpacking, vacation traveling, etc.
What more can one say of the product? I dare add that given the anemic battery included with the EOS-M, Canon would have been well served to have made a powered version of this adapter for the EF lenses. Battery life really suffers when mounting Canon's larger offerings on the M using this baby.
I love this adapter, metal construction and a build worthy of L lenses. I have been using this adapter with the 70-200 f4l and it is a joy to use, it has a quality feel befitting the L series lenses and a finish that matches, back up a bit and you wouldn't really notice there is even an adapter attached on the non-white lenses.
I have a few L lenses that I use for my 5D so this was a great addition for the EOS M. Works and fits well just like most Canon product. I would not suggest this if you do not have any other canon lenses as you should save your money for the lenses made for the the EOS M. The crop sensor factor must be factored when using regular EF lenses.
The adapter was immediately a huge part of the EOS M camera purchase. I highly  recommend it if you have other lenses. Again, the results I got with the EF-S 60mm macro (and studio lighting)  were stunning. It transformed the camera from curiosity to studio prime. No problem using manual mode and Pocket Wizard. Include this adapter in your purchase and you won't be looking back.
This adapter is very well made and works well in using Canon EF and EF-S lenses on an EOS-M. Based on the recommendations of others, I paid the higher price for the Canon adapter rather than buying the third-party brand. The tripod mount on the bottom of the adapter is very useful in balancing the camera and the lens and is perfect for use with the Opteka HG-1 Heavy Duty Aluminum Grip which gives you solid, stable control of the camera and lens.
Canon EOS-M firmware v2.0.2. I used this with the Canon 135mm f/2.0L USM today, from an open-roof tour bus, which was stopped for most of the shots. Effective focal lengths of 216mm. It was a bright cloudy day and 99% of the 106 images I took of a variety of architecture and statues were excellent focus. At f/5.6, shutter speeds were 1/2000s.
Works with all my EOS Lenses. Saved me from having to buy new lenses for my EOS M camera. Must have..
Answer: I used my old 30D lens with the adapter, a 75 to 200 and a 300 zoom, and the auto focus is really slow and noisy.. But I never use auto with video anyway.. Lock in the shot, and go. I use manual..