Hi Godfrey,
I presume you are talking in 35mm Equivalent Focal Length Speak since thre is no "Olympus 35mm" or "Panasonic 40mm" for Micro-FourThirds.
Obviously.
I prefer to think of focal lengths as being attributes of the lens. It's less confusing. A normal lens focal length is dependent upon the format, translating everything through the perspective of a 35mm format is very often a major confusion point.
Sure, but I didn't mention them because I forgot them. I was thinking about the mirrorless systems. You can use them, but the 25/f2.8 pancake doubles in size when mounting it on an adapter ring that then goes onto the µ43 body.
It's still small and light weight even then. The ZD 25mm f/2.8 makes an excellent normal lens for the Micro-Fourthirds cameras.
I think that limitation was taken out of µ43, but I'm not sure. The requirement to have the light coming out of the lens nearly perpendicular to the sensor has also been toned down, IIRC. I also think that I read the rumours sites too frequently !
Micro-FourThirds and FourThirds sensor size is the same. If you draw a conic section starting with the image circle required to cover the sensor, with the included interior angle fixed by the FourThirds lens mount diameter at 38.5mm register distance, you'll find the smaller lens mount diameter of Micro-FourThirds fits at exactly 19.8mm on that conic section. QED, the same mount design for an f/1.4 lens speed is in place. You can fit faster lenses on either, but there is a limit to the benefit that can be gained from doing so.
The
"requirement" for ray trace perpendicularity at the plane of the sensor hasn't relaxed at all. It was never a requirement, per se, it was a theoretical ideal and it still is. However, modern sensors have shallower photosite wells than sensors that were bleeding edge at the time that the FourThirds design ideas were being formulated. This fact, and the combined effects of FAR more in-camera processing power, more sophisticated image correction algorithms, lens correction metadata injected by the lens to aid corrections on a lens by lens basis, etc etc, have all combined to make Olympus and Panasonic a little more relaxed about ray trace perpendicularity ... With modern sensors and the corrections to the image data that can be applied nowadays easily, the effect is that the sensor can tolerate a couple more degrees of deviation from perpendicularity, allowing lens designers more latitude to produce smaller, simpler lens designs that perform as well. The shorter mount register helps a lot too.
Yes, everyone on these forums read the rumor sites too much. I don't hate them, but I find them mostly a source of misinformation inspiring endless pointless nattering on the discussion boards.