My impressions of the Metabones Speed Booster; a special adapter for Canon EF lenses to Sony NEX camera bodies.



The Metabones Speed Booster Canon EF to Sony E-Mount Adapter

The Metabones Speed Booster is a new concept in lens converters. It actually helps to think about this new gadget as the reverse of a teleconverter. Whereas a teleconverter increases the lens effective  focal length and loses one or two stops of light in the process, a speedbooster does the opposite; it shortens the effective focal length and increases light gathering by one stop (when used on a APS-C camera). As an example, a 50 mm f/1.8 lens on an APS-C camera effectively behaves more like a 75mm given the APS-C 1.5x crop factor. When using that same lens with a Speedbooster, the equivalent 50mm focal length is restored but we gain an extra stop of light as the maximum aperture is now 1.8/1.4 = 1.2. It's such a great idea that one wonders why Metabones was the first to implement this! More on that later...

I rented a Metabones for a weekend and experimented with my Canon full-frame lenses mounted on a Sony NEX-5N (since replaced by the NEX-5TL and NEX-6) camera body. Figure 1 shows my Canon EF 50mm f/1.8 (that becomes a f/1.2!) mounted through the adapter. This is a modest lens in the Canon line-up, but capable of remarkably good results. It's also small, fast and very light, so it's a good match to the tiny NEX camera body.

mounted camera

 Figure 1 - Canon EF 50mm f/1.8 mounted on NEX through Metabones adapter

During my time with this adapter, I also experimented with a Canon EF 100mm f/2 and a EF 35mm f/2. I should note that the Speed Booster does not work with EF-S (crop) lenses; only with full frame lenses such as the ones listed. This makes sense when you consider that the gain in light gathering ability comes from concentrating a full-frame area into a smaller APS-C sensor area. Therefore, you need to start from a larger, full-frame lens for this 'trick' to work. Also note that, although the Metabones supports IS and auto-focus operation, the latter is not supported for all Canon lenses, including unfortunately the three primes I tested. In any case, all the reports I've seen indicate that this is a very slow auto-focus option (contrast only) so you are better off using manual focus anyway. So, with these preliminary comments out of the way, here are my impressions of the adapter:

- Image quality including both sharpness and bokeh are surprisingly good when using the adapter. This was of course a concern since the Speedbooster adds another glass element in the light path. However, this seems to be a very well engineered piece of glass, and I saw no obvious image degradation. In fact, because of the wider effective aperture, the bokeh can look better than when using the original lens alone.

- Build quality is excellent. This is an all-metal adapter and all materials seem to be of good quality.

- The electronics in the adapter communicate well with the Sony body, so you get correct aperture readings, aperture control, IS (when supported by the lens) and EXIF data in your image files.

- Manual focus is aided by the "focus peaking" feature in the Sony cameras but it still isn't all that easy. I use fast lenses (now even 'faster' with the 'boost') primarily to shoot portraits. I like the shallow depth of field (bokeh). While the bokeh is indeed improved by the adapter, manual focusing is quite slow and at times frustrating. I missed using these lenses in their original, auto-focus capable Canon cameras. Also consider that these EF lenses were designed primariliy for auto-focus operation, so the manual focus rings are not that smooth nor precise (the EF 100mm f/2 was slightly better than the others in this regard).

- Canon Full-frame lenses (required for Speed Booster operation) are usually larger and heavier than the native Sony E-mount lenses. They can be ackward to mount and operate on a small NEX body (in this regard, the EF 35mm f/2 and  EF 50mm f/1.8 fare better than the EF 100mm f/2).

- The lenses behave at their 'native' focal length (i.e a 50 mm looks like a 50 mm on full-frame again). This can be very helpful in the wide-angle side of things, and may be a disadvantage if you need a telephoto. Either way, you now have a lens that can be used at two different focal lengths depending on the adapter you use. This is very nice.


Figures 1 and 2 show two of my favorite portraits I shot using the Metabones and the lenses listed. Notice the bokeh quality and sharpness seem pretty good even with the adpater mounted.


 Figure 2

Sony NEX-5N, Canon EF 50mm f/1.8


Arlene 1

Sony NEX-5N, Canon 100mm f/2, Metabones Speedbooster


Conclusions and Future Developments

In conclusion, the Metabones Speed Booster is capable of delivering very good results and gives you a much welcomed gain in light gathering ability. Would I buy it? At this price point (currently it sells for about $600) I would have a hard time justifying it's purchase. Manual focusing (or using the slow contrast auto-focus) can be challenging for the portrait work where I would most likely use it. If the price came down by half, I might consider it. That said, one has to applaud Metabones for this truly inovative product; a product that delivers exactly what it promised to do.
I wrote at the beginning that I didn't understand why nobody came-up with this idea earlier. Surely the likes of Canon, Nikon, Sony, Sigma, Tamron etc. can design something like this. Maybe there are technical issues related to the lens to sensor distance in designing such an adapter, but with an extra lens element in the path, perhaps those can be overcome. I suspect this is not so much a technical difficulty as it is a market decision (and perhaps there are legal licensing issues too). Imagine for a moment that Canon released an adapter like this one and allowed us to use EF full-frame lenses on Canon's APS-C bodies with a 1-stop gain in speed. Suddenly, all these affordable f/1.8 and f/2 lenses would compete with their super-expensive (read very 'profitable') f/1.2 and f1.4 lenses that sell for two to three times the cost. I personally would love to see Canon (or someone else) come-up with such a product. The lenses would remain in the same camera system, so one could expect auto-focus to work properly. You may say I'm a dreamer but, as John Lennon said, I bet I'm not the only one...

Comments, questions, suggestions? You can reach me at: contact (at sign) paulorenato (dot) com