New photographers are often surprised by how much maths is involved in photography. I’ve never been one to shy away from maths, actually, I was always good at it in school (my parents
hoped thought I’d been an engineer!). Anyway, I understand most of the technical side of photography, the ratios, inverse square law, blah blah blah. But today I got stumped on trying to understand, and then explain, the mystery of the Speedbooster. So I’ve made myself this little pictorial “cliff’s notes,” so to speak.
Take full frame lenses (specifically Canon and Nikon, in this case) put them on Micro Four Thirds cameras like Olympus and Panasonic and they have 2x crop factor. Then there is an additional 1.2x crop factor of 4k video. This makes for a 2.4x crop factor on 4k capable MFT camera such as the popular GH4, turning your 24mm lens into a 58mm. So Metabones comes along with these awesome adapters called Speedboosters that restore some of that crop factor while increasing the intensity of the light reaching the sensor. The first generations decreased the crop factor by .71x (2.4 x .71 =1.7) making that same 24mm a 40mm, also taking an f/2.8 aperture to f/2.0 (1 stop gain). A new .64x version of the speedbooster decreases the crop factor further (2.4 x .64=1.5) making that 24mm lens a 36mm with an aperture of f/1.8 (1 1/3 stops gain).
Dizzy from all the numbers? So was I. So a very curious and patient client (Thanks, Jordan!) and I decided to run a quick test in the store. We set up a GH4 using a marker on the counter to keep it in the same place and took 3 images of a set up of random stuff on the counter. In hind sight, I could have chosen a less cluttered background and a prettier setup, but this serves its purpose so please forgive the camera shop mess. We used the Lumix 12-35mm lens and then the 24-70 Canon lens with both the .71x and .64x Speedboosters, and I used a second camera to take these screenshots. Note the changes in angle of view (how much of the edges are cut off) and the aperture changes on these 2.8 lenses.
The .64x XL version of the speedbooster has a larger protrusion into the camera and can BREAK the shutter if used on an incompatible camera. That means DEAD CAMERA! Please make sure your camera is compatible before trying to use it.