A7r - The reason all the new FE lenses are too big.

[fractal]

Blame the A7r.

Sony’s Master plan – new 85, 24-70, 70-200 and more

"It’s all down to the A7R 36 megapixel sensor. This sensor, more so than the 24 megapixel full frame, requires a very telecentric lens design. That is, more like a DSLR lens, despite the slim A7 series body. In order to perform acceptably with this sensor, the FE lens range could not be designed to be as small as a rangefinder system equivalent, or to take full advantage of the 18mm mount to sensor distance.Brian Smith, whose images are great (not cheesy portraits) but whose technical info clearly comes via Sony PR, says this: “Mirrorless camera design has allowed Sony’s lens designers to place larger than normal lens element close to the body”. Actually, they don’t, as the design of the extenders will tell you. They’ve used a stronger degree of telephoto construction in the long zoom, allowing a smaller than normal rear element and they have taken measures to move it further away from the body – and this is a general trend. If you want to see what a properly small 85mm f/1.4 looks like try a Carl Zeiss Planar 85mm f/1.4 ZE in Canon mount – 72mm filters not 82mm, 570g versus 850g and really solid all-metal manual focus. The mirrorless bodies do provide a zone from around 16mm to 42mm from the sensor surface which can accommodate the rear of the lens, and can’t ever be used on a DSLR. But Sony does not make full use of that and can not do so because of the microlens, filter layer and structural characteristics of the A7R sensor."

 

[pbizarro]

Yup, even the new and recent f2.8 zooms from Canon and Nikon are 82mm lens diameter: 16-35, 24-70. If you want high rez sensors and top performance, that is what it is.

 

[JonathanF2]

I think Sony should of put more forethought into the E mount design. I think a bigger diameter bayonet mount and a slightly longer register distance would of helped in shrinking the lenses down a bit. The Fuji X mount has a slightly shorter register distance, but the sensor is better sized to the mount which results in more evenly designed lenses.

Another option is to follow the 4/3 sensor ratio and cut the sides off, optimizing the lenses for a square'ish format. That could probably also shrink lenses down a bit as well.

Though I'm no optical engineer so take my opinion with a grain of salt!

 

[fractal]

Yup, even the new and recent f2.8 zooms from Canon and Nikon are 82mm lens diameter: 16-35, 24-70. If you want high rez sensors and top performance, that is what it is.

From the article;

"All Sony FE lenses and all CZ independent FE lenses have been designed to work well with the A7R. The 28-70mm kit lens was not, but most owners find it acceptable. They could have made some of the lenses a fair amount smaller and lighter if the A7R had never existed. The A7RII is so tolerant towards short back focus, oblique ray angle imaging, that a whole different range of lenses could be designed for it… but never will be."

It seems the A7r sensor needs a DSLR type lens, while the new 42mp sensor could do just as well with smaller "rangefinder" type lenses.

 

[storyteller]

Testing has also shown that the relatively thick sensor glass also causes problem but perhaps this is less of a big deal if designers take it into account.