Lens optics experts: does mirrorless (e.g. MFT) allow smaller actual lenses?

Started Jan 25, 2012 | Discussions thread
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Rehabdoc
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Lens optics experts: does mirrorless (e.g. MFT) allow smaller actual lenses?
Jan 25, 2012

I know the promise of MFT is a smaller total camera. You get rid of the mirrorbox, which wipes out a large amount of in camera volume, and lets you have a much shallower camera. Also, mirrorless using a side-placed EVF (if you do it like NEX 7, not MFT, but no reason MFT couldn't use that design) lets you knock something off the height as well.

My question is whether removing the mirrorbox and thereby shortening the minimal allowed distance between sensor and the rear element of the lens (compared to a DSLR) actually allows for

(1) smaller lens of the same parameters (focal length, zoom power, macro, f-stop)?
(2) easier to design lens of the same parameters?
(3) less glass in the actual design of lens of the same parameters?
(4) shorter collapsed size of lens of the same parameters?

I understand basic optics, but don't know much about real camera lens design (e.g. i have no idea whether in a real camera, in a zoom or fixed focal length lens, the rear element of a lens changes distance from sensor during focusing and zoom operation, or not. I suspect the answer is usually no for the fixed, and maybe for the zoom).

Does, for example, an F2.0 continuous 80-200 mm zoom, become easier to design if you can place the rear lens element closer to the sensor? Or not? How about macro or fisheye?

Obviously the SLR's mirrorbox NOT allowing the lens close to the sensor is TECHNICALLY a design constraint... but is it not a REAL problem in the real world lens design? Or is it not, because, let's say, the lenses we use are typically bringing focused light perpendicular to the sensor plane?

It seems like putting a rear element closer to the sensor plane WOULD alter Bokeh. For good or bad I don't know, but with the same f stop, focal length, etc., the Bokeh could be quite different at the same f-stop... or am I wrong about that? I'm guessing.

I know some of my knowledge gaps are basic to camera optics, but I just want to know HOW MUCH more compact can MFT lenses theoretically become compared to SLR lenses, apart from the issue of the mirror box distance. Or can they really become much more compact than SLR lenses at all?

Any real world lens experts able to educate us?

Sony Alpha NEX-7
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