No SLR lenses have that as well. Even my decades old Sony a65 had that .
Mirrorless lenses CAN be made smaller compared to what we’ve been used to from the SLR era.
The question is if that really happens. Or if lens makers use the weight to improve the quality of the glass (since modern sensors are more demanding for pixel peepers) .
A Tamron 70 to 180 2.8 e-mount is a massive difference in size and weight compared to the Sony a-mount 70 200 2.8 which i also still own . I call that lens 'the beast ’ (while i know 150-600 lenses or 400mm f4 lenses are even bigger).
Does the size/weight benefit come from more modern lens building? The 20mm missing at the long end ? Or the fact it’s for a mirrorless mount?
I don’t know. Probably all of the above. I do know i actually like taking the 70 180 with me, and i can’t remember the last time i used to 70 200 a-mount beast. It handles like a SLR style 70-300 f4-f5.6 ‘starter lens’, but gives you f2.8 . I think it’s awesome when you compare them.
But… To counter my own findings. As a smaller camera i went with an Oly omd em10 mark1. I loved how small it is, specially with a cheap entry level pancake lens. And I picked it because I wanted something that still gives me the 'photography experience’s , like back button focus , viewfinder , custom settings , etc…
But for a small camera ,the Oly has some metal elements and is heavier then ii think for its size.
Now, i replaced my Sony a65 SLR for a Sony a7mark2 some time ago . And that Sony a7 with a cheap entry level pancake lens… Did make me stop using my Oly for a while, because the Sony combo was actually not really different in size and weight !
I basically only use entry level lenses for my Oly (since i see it as the cheaper lighter 2nd camera). And i love that i can pack my whole kit in a little 9" camera insert. Body, effective 28mm pancake , effective 35mm pancake, effective 50mm, effective 90mm, pancake collapsible default kitlens, and a very small and light effective 85-300 entry level zoom . That whole kit fits in the same size as my Sony a7 with a 85mm 1.8.
So, i don’t think the mirrorless aspect is the real space saver, it’s more the thing if you want the best of the best or allow yourself to use cheaper and slower glass.
Still … my Tamron 28-75 2.8 e-mount lens is a bit smaller and quite light compared to my old 17-50 2.8 APS-C only a-mount lens . So steps have been made ! (Higher quality , full frame , smaller/lighter vs the older. But a no-compromise Sony 24-70 2.8 will be huge no matter what ).
and this makes it of course harder for the camera).
