Micro Four Thirds
An open sensor and mount standard using a 17.3 by 13 millimetre sensor with a 4:3 aspect ratio and a 2× crop factor.
Formula / rule
Crop factor = 2.0
Measured in
mm
In depth
Designed from the outset for mirrorless bodies, the standard has a short flange distance and telecentric lens designs, so its optics are unusually compact for their performance. The two-stop light disadvantage against full frame is real, but so is the two-stop depth-of-field advantage when everything must be sharp, and the size saving on long lenses is dramatic.
Examples in practice
A 300 mm Micro Four Thirds lens frames like 600 mm on full frame yet weighs under 1.3 kg.