Image courtesy: Diglloyd.com
Lloyd Chambers created a sort of a camera obscura to make a more accurate measure of the image circle of FT and MFT lenses. As you may know Four Thirds sensor have a diagonal of 21,6mm while APS-C sensors have a diagonal of 28,2mm. The question is if current FT and MFT lenses would cover a larger than FT sensor. He first tested the superb 14-35mm f/2.0 FT zoom lens. Wide open the lens has a circle of 26mm which increases up to 32mm on the tele end.
He also tested some MFT lenses:
Panasonic 25/1.4 has a 27mm image circle
Panasonic 45/2.8 macro has a 25mm image circle
Olympus 45/1.8 ED has a 31mm image circle
Olympus 75/1.8 ED has a 29mm image circle
In theory the two Olympus MFT prime lenses would cover the full APS-C sensor. Doens’t necessarily mean Olympus did it intentionally. But it’s interesting to know!