Comparing the new Metabones 'Speed Booster' with 'The Original' NEX2EF adapter.
From this 'Very Late Christmas shootout' you can compare the two adapters for yourself. The new one gives you indeed more f-stop. The detail is indeed better. But for me it's all about going wide. What's the point in buying a Full Frame lens when it only can give you a small part of it's potential. A FishEye is a super wide lens, it's not a bad 28mm lens. The Canon 50mm f1.4 will never be a great 85mm portrait lens. So this new adapter is a wonderful solution for using Full Frame lenses on a Super 35mm sensor.
It this short 'shootout' you can see the difference between the two adapters. All the shots are taken with a different f-stop (2.5-2.8). When the camera is set to f2.8, with the new Speed Booster the lens is not to that same value. In reality with the 'Original' adapter you are shooting at f2.8. With the speed booster your lens is set to a higher number, something like f3.5. Just to compensate the extra light. In this video the shots with the 'Speed Booster' seems to be darker, but this is just a side effect of the fact that the f-stop is not the same for all shots.
All footage (MTS files from the Sony NEX FS100) and some extra raw NEX-5 photos can be downloaded via the instructions mentioned in the video.