I currently live in the Canon ecosystem, but really like the look of the Sony a7S. But before I switch I want to know just how well I'll be able use use my old EF-mount lenses on my new a7S.
How well do the mount adapters perform?
Are there any converters that would allow me to use my old EF lenses with 100% of the original functionality (auto-focus, IS, EXIF data, etc)?
I would not normally ask, but this isn't the sort of thing I can try out in the store.
Yes, there are adapters with full function (the pretty expensive Metabones adapter springs to mind) so you'll have aperture control, but the AF performance won't be anything near what you're used to on EOS mount. To quote from their website for the Mk III EOS->E adapter:
Autofocus is supported, with the following known limitations.
Autofocus speed is very slow and inadequate for most moving subjects. The autofocus speed is unfit for professional use for sure, and it would disappoint most enthusiasts. Only Canon-branded lenses introduced in or after 2006 are officially supported. Autofocus may be disabled for older Canon lenses and most third-party lenses, including most Sigma, Tamron and Tokina lenses and all Contax N lenses modified by Conurus. ...
Along with a whole mess of other caveats. So, practical upshot, you'd probably be better off trying to adapt manual-focus lenses that have an aperture ring on them. Much simpler, easier, and pretty much the same (or more) function. And if they're rangefinder lenses, then the size/weight is closer to ideal.
In the mirrorless world, to me if you're a Canon L shooter, if you're willing to sacrifice sensor size for lens selection, you go µ4/3. If you're happy to sacrifice lens selection (and speeed) for full-frame, you go Sony A7 system. And if you're happy with APS-C and fast expensive glass, then you go Fuji X.
The Sony A7 models are particularly problematic, given how there's a lack of full-frame lenses for it from Sony, they tend to be very expensive, and adapted rangefinder lenses--particularly the Leica M wide angles, have questionable performance, quite possibly due to the sensor stack thickness. In addition, to keep size and weight down, most of the full-frame E lenses are f/4, but have f/2.8 L lens prices. Best to make your peace with that before getting an A7, in my book.
Roger Cicala of lensrentals.com is less than enthusiastic about converters in general, http://www.lensrentals.com/blog/2013/09/there-is-no-free-lunch-episode-763-lens-adapters, and if you follow the link you'll see why- they can very often reduce image quality, even though they have no glass elements in them.
Recently I tried out the Sony A7s II in a camera shop with these four adapters (ordered by price, high to low):
and these two Canon lenses:
Same as the Metabones.
- Canon to E-Mount - Viltrox EF-Nex II Auto-Focus adapter -
I own a "Sony A7 II", I still have a "Canon EF 16-35mm F4L IS USM" and a "Tamron SP 24-70mm F2.8 Di VC USD" from the Canon equipment that I used before.
So I bought a "Viltrox EF-Nex II Auto-Focus Canon to Sony E-Mount Adapter" to use these lenses on my Sony body.
1st of all, the AF is really slow and searches a lot compared to when used on any high-end Canon body ... and that's the BEST case scenario imaginable.
What often happens is that the Canon lens to Sony A7 body is a rather LOOSE ASSEMBLY due to the poor machining and precision of the Viltrox adapter. IT IS LOOSE ALL THE TIME.
The result is that quite often, the lenses fail to transmit aperture data to the body, and you need to turn the camera OFF, unmount the lens and adapter, mount the lens and adapter back again, and turn the camera back ON (just nerve wrecking) ... AND BE VERY CAREFUL NOT TO "ROTATE" THAT LOOSE ASSEMBLY WHILE YOU WORK AROUND THE LENS.
Quite frankly, you are better off working with Sony lenses, even if some of them may have a tad less performance compared to some high-end Canon lenses ... and some third-party lenses specifically designed for the E-Mount system will also be a lot more satisfying than the "Canon to E-Mount assembly".
Well-known brands (Canon/Nikon/etc) don't share their "proprietary MOJO and compatibility standards" with other companies (such as companies dedicated to the "lens adapters domain").
As a matter of fact, adapters should include a complete ELECTRONIC INTERFACE in order to precisely translate the Canon/Nikon/etc electronic standards to the E-Mount electronic standards back and forth ... and that also means that these adapters should be POWERED in some way.
WELL ! THAT SAID !
I still managed to shoot a couple of great shots with my Canon lenses mounted on the Sony A7 body. You can't be unlucky all the time.
