Micro Four Thirds
Micro Four Thirds is a 17.3x13.0mm sensor size and, unusually among formats on this site, a jointly developed, shared lens-mount standard — OM System (the successor to Olympus's camera division) and Panasonic both build bodies and lenses to the identical specification, so lenses from either brand mount and function on bodies from the other.
Its crop factor computes to almost exactly 2.0x, the cleanest round multiplier of any format this site covers, which extends telephoto reach dramatically for a given real focal length — a major reason wildlife and birding photographers favor the format. That same physical size gives it a stricter circle of confusion than full frame, meaningfully more forgiving depth of field once framing is matched between the two.
Frequently Asked Questions
Can I use an Olympus lens on a Panasonic Micro Four Thirds body?
Yes — that's the entire point of the shared standard; lenses and bodies from either manufacturer are mechanically and electronically compatible, with only minor feature differences depending on the exact pairing.
Why is Micro Four Thirds' crop factor so close to exactly 2.0x?
Its real 17.3x13.0mm diagonal happens to divide into full frame's 43.27mm diagonal almost precisely by 2, a genuine, deliberate outcome of the format's original dimensions rather than a rounding convention.