Rocky said:
Talys, I am just giving you the technical information of the limitation and advantage and of the EF, EF-S and other shorter mounts. I have not avocatingany new mount yet. As for proffessional lens must be big and large, I will strongly disagree. Have you looked at the Lieca 50/0.95? As for tapppered lens, Canon is just doing that on the 50/1.2. Which optical book that you have found the term "flange focal distance"? The only reason why almost all lenses have the rear element recess into its own mount is to protect the rear element. May be Canon should pay Leica royalty to do off-set micro-lens and start building smaller shorter focal length lenses for their FF mirrorless camera and use adapter for the longer EF lenses with the new FF body.
Rocky, I'm not disagreeing with you at all from a technical design perspective. The truth is that I am absolutely no expert at this, with not even a fraction of the knowledge of many of the regulars of this board. I don't even have the engineering curiosity to want to learn that. All I go by is my observations, which don't include Leica lenses other than what I've seen on forums, because I don't have any friends with Leica equipment.
When I posed the question about mount design, I was looking for someone who has more knowledge than me to indicate what Sony is doing wrong, and what Canon could do right, to result in a full frame package where the total size is a significantly smaller, including the most popular zooms and primes that a lot of us own. It is unhelpful if that includes lenses that are missing things like IS and certainly AF, because this is something that the overwhelming majority of the customer base wants, so I think that Leica is a poor example anyways. In other words, if you want a Leica, buy a Leica, because nothing else is really like it.
All I have to go on myself is my observations of Canon, Sony, and Nikon lenses, and how the lens + camera package doesn't vary by much.
Also, I didn't say that there weren't ANY professional lenses where the distance between the sensor and the first glass element couldn't be shortened, only that this is the case with most of them, and certainly nearly all of the best-selling pro/enthusiast zooms by every major full frame manufacturer.
From my (limited) understanding of lens design, the optical formula is the optical formula, and requires a certain distance between the first glass element and the sensor. Unless there is a different formula where that is shortened, any space you take out from between the edge of the mount to the sensor needs to be added back in to the space between the start of the lens and the glass. My understanding is that the existing optical formulae are pretty good, and while there can be tinkering around the edges, the only really significant innovation to shorten the length of lenses has been diffractive optics, which isn't necessarily useful to all focal lengths, and apparently, can't be done on the cheap.
Finally, regarding the 50/1.2 design. Yes, it tapers to the mount. And if you really want to push it, you can say that every superzoom also tapers towards the mount. My issue isn't with the taper (what do I care what shape the lens is?); it's with the taper interfering with my fingers, because (a) of how quickly it flares out and (b) the positioning of the grip.
If the camera body designer of the A7/A9 simply added a half inch between the camera mount and grip, I wouldn't care about the taper in that direction. And if the camera body designer likewise added a half inch vertically so that a part of my wrist didn't bite against the bottom of the camera without a grip, I wouldn't care about that, either.
But that isn't the case: the reason to build a smaller mount (for Sony) was to shrink the camera body in the Alpha to the minimum size possible. The net effect is that the camera becomes, for me, very uncomfortable -- without having any significant benefits, because all of the small lenses that fit on the 46mm throat with short FFD are not lenses that I want to own.