James Miller reports on the Metabones Speed Booster – an optical reducer that reduces the projected image of a lens to counter the cropping of smaller sensors. The results are improved lighting performance, sharpness.
In essence, it’s an optical adapter that attaches to the E mount of a Sony NEX camera (Super 35 sensor) and then to a full frame SLR lens. The Metabones ‘Speed Booster’ is a 0.71 x focal reducer, that will effectively turn your full frame 50mm f/1.8 lens into a 35mm f/1.2 lens. Note, doing so (as a guide) will increase the aperture of that lens by one stop. Your Sony NEX Super 35 E-Mount will effectively have near full frame coverage on a full-frame lens. It also serves ‘double-duty’ as a lens mount adapter, from Canon EF lens (but not EF-S) to Sony NEX, with auto-aperture and image stabilisation.
It’s not just for really fast lenses – for example, a Canon 17mm f/4 TSE now becomes a 12mm f/2.8 ultra-wide tilt shift. I myself am still building a lens collection, and whilst the super fast Canons due to cost are not in my personal arsenal, my slightly slower Canons and Nikons have just been given a speed boost. That’s great news.
Here’s another article on the subject that may shed a little more light on how this works:
First understand that a lens simply projects an image over a flat surface. The image has a circular edge, we call it the image circle. The rectangular sensor sits inside that circle and then produces a digital image from the light falling on it.
So imagine a full frame sensor and the lens projecting a circle of light onto that box… The image is large enough to cover the full frame sensor. A smaller box inside that would not see the edges of the image circle or the full field of view.
How is that possible? The glass in the new Metabones EOS/E-mount Speed Booster adapter is an optical reducer. This glass is already common on some astro-telescope camera adapters to shrink the telescope’s image to fit a digital camera body.
The side affect of this is that it is actually brighter, like in the way a projection beam gets brighter as you move the projection lens closer to the wall. The image gets smaller and more concentrated.
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