Originally posted by Wheatfield A mirrorless APS-C camera with K-Mount and a viewfinder will not be significantly smaller than a K3. Much of the size of the camera is dictated by the registration distance the large battery and in body image stabilization.
I both agree and disagree with this. The depth from the adapted K-mount to the rear of the camera wouldn't be much different (if at all), but the rest of the camera's dimensions can be considerably smaller if required. The lack of viewfinder prism and separate phase detect AF module alone allow for considerable space saving.
Compare Sony's A7 series, fitted with LA-EA4 AF adapter, versus the Sony A99 or A99 MkII. These are full frame cameras, of course, but the comparison is still a valid one. And all but the earliest A7 "Mk I" have in-body five axis image stabilisation. In fact, these full frame cameras with articulating screens are significantly smaller than the APS-C K-3 / K-3II. The APS-C A6x00 series cameras are smaller still.
Smaller size, however, doesn't always equate to great handling. Personally, I'm happy using my bigger A-mount lenses (Tamron 70-200 f/2.8 USD, Tamron 150-600 G1) on the A7II + adapter, but it feels very different to using a larger camera, with almost all of the work being done with the lens arm, rather than a combination of both left and right. That works well for me, as my right arm is problematic with rheumatoid arthritis, and I'm right-handed - so I may be a little biased
But the combo is less well balanced in my view, compared to a bigger, heavier DSLR plus lens.
Of course, when you start using (some, but not all) native mount lenses, or adapted lenses for systems with smaller flange focal distances, the combo size advantage can be more compelling still.
The biggest disadvantage, assuming you can live with an EVF (personally, I can - and actually like them), is - as you've rightly pointed out - battery life, which is dire by comparison. Small batteries and constant "live view" isn't a great combination... think "Pentax KP" running in Live View
all the time The accessory battery grip is more-or-less permanently attached to my A7II... making it not such a small camera after all (though rather nice to handle).
Last edited by BigMackCam; 02-02-2018 at 01:08 PM.