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

Started Dec 18, 2013 | Discussions thread
TrapperJohn Forum Pro • Posts: 16,488
Two reasons Leica M glass is so small

Leica M is pure manual operation.  This eliminates two features common to all DSLR glass, both of which add size.

No autofocus, so no autofocus motor, gearing, electronics, or connections.

Leica M also doesn't have any form of external aperture control. Since it's a rangefinder and doesn't use a TTL viewfinder, there is no need to externally control the lens aperture (leave wide open for viewfinder use, stop down to selected F stop when shooting), so no external aperture control mechanism. Even the earliest film SLR's had external aperture control on their lenses so the VF didn't go dark when the photog stopped down.

Those are two big reasons Leica M glass is so small, neither of which relate to registration distance.

As for shorter registration distance making the lenses smaller... don't know about FF, but with 4/3, the shorter reg distance did not make the lenses smaller. Compare the kit grade 4/3 ZD 14-42 and 40-150  to their functionally identical M43 counterparts - they're about the same size, except the 14-42 uses a 'folding' design to make the lens shorter when not in use.

There is a size reduction from the fast HG and SHG ZD glass to the Panny constant F2.8 zooms and MZD Pro lenses, but again, not directly related to registration distance. The 4/3 HG and SHG glass have a telecentric design: straightens the light out in the lens to eliminate edge problems, whereas the Panny and MZD Pro don't appear to use a telecentric design - a thinner sensor with shallower light wells was used to handle light at angles better.

The telecentric design resulted in a much thicker lens barrel - compare the ZD 12-60 to the MZD 12-40, main size difference is the 12-40 has a more slender lens barrel. Same is true, somewhat, comparing the ZD 50 F2 to the MZD 45 1.8... much thinner lens barrel, though the 50M's macro design probably contributes somewhat to its thicker barrel.

The A7 has to be a commercial success before third party lensmakers will even try to size optimze FF glass for it - what I see now looks like standard Zeiss designs with just a shorter reg distance. But, the A7 probably won't be a commercial success without truly size optimized FF glass, as M43 did.

My personal guess is - the concept and marketability of a truly small FF system has been proven, but it will take a serious photo company to make it successful with not only a small body, but a decent range of size optimized glass.

Nikon, Canon, here's a chance to hop in and join the party.

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