Michael Reichmann's take on smaller full frame Sony FE mount lenses

Started Dec 18, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Michael Reichmann's take on smaller full frame Sony FE mount lenses

FrankS009 wrote:

In a recent piece,


Michael Reichmann wrote,

"A lens has to be of a certain size to cover full frame. That size is now smaller than it used to be, because FE mount lenses don't have to have the large rear register distance that ones designed for DSLRs did. By way of comparison have a look at Leica M lenses vs. SLR lenses. They have always been considerably smaller. Compare the size of a 35mm f/1.4 Summilux, for example, to a Nikon or Canon 35mm f/1.4. The implication of this is that the size and weight disadvantage of digital full frame is rapidly disappearing. And if I were a manufacturer committed to the Micro Four Thirds format I'd be looking over my shoulder nervously. Very nervously!"

Would someone please explain this to me. Is it possible to be more explicit about size and weight of FE mount lenses than Reichmann is?

A short flange (register) distance makes it easier to design small lenses on the WA side. If the focal length is shorter than the flange distance (which is approximately 45 mm for FF DSLRs but only 18 mm for Sony FE-mount), the lens has to use a so-called retrofocus design, which makes it bulkier and heavier. See here for an explanation of the retrofocus concept:


On the other hand, what Reichmann says about Leica M lenses is a bit of a red herring. The Leica M (and other rangefinder) WAs were originally designed for film and their lack of telecentricity is a problem with digital sensors since the light destined for the edges of the sensor has a fairly large angle of incidence. This may cause problems with vignetting (due to poor utilization of the light that comes in at such angles) as well as edge sharpness and purple color casts (due to crosstalk). Leica is now forced to work around these problems in various ways. These digitial-specific problems aside, the old rangefinder WAs also have problems with so-called natural vignetting. See here, under "Natural vignetting" for an explanation:


For these reasons, I wouldn't think Sony/Zeiss will want to use old rangefinder designs as a blueprint for their FE-mount WAs.

But let's go back to the more general question of whether FF lenses can be made about as small and light as MFT lenses having the same angle of view. If the FF lens is to be as fast as the MFT lens in terms of f-stops, my answer to that question is a simple no.

If, on the other hand, the FF lens is made two stops slower, so that it becomes equivalent to the MFT lens with regard to light accumulation, DoF, and diffraction, things become a bit more complicated. My answer would now be yes, provided that the FF camera has a short enough flange distance (as Sony FE-mount cameras do) and we are talking about WAs and normal lenses, possibly even short teles. Longer teles would still be significantly longer for FF than for MFT at the same AoV although not necessarily heavier, at least not much heavier.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow