Do portable fully automated DSLR lens-changers exist?
If so, how well do they work and how do they compare with alternative solutions.
I've seen many "lens bags" offered to ease the lens changing and carrying issues. Those are not what I want.
This is not a "shopping question". Read on ...
"When it matters" I carry two and sometimes three DSLRs. TAs well as backup capability this allows the 2 or 3 most useful lenses to be available almost instantly. However, my secondary cameras are of lower specification than my main camera and the extra weight and general encumbrance is undesirable in many cases.
If I could change lenses on my main camera with essentially no time penalty it would allow the use of one active body and the lens changer and lenses, with a secondary body able to be stowed rather than flapping in the breeze.
A look through internet offerings did not reveal anything made for portable DSLR use - "lens changing robots" for laboratory use were available.
Do they exist? How well do they work? What are the pros and cons?
Obvious question - if I made them would they sell?
With modern electronics and compact motors, a changing robot is not hard to envisage.
Needed tasks are: unlock, rotate, withdraw, stow, acquire new lens, move into position and alignment, insert, rotate/lock, declare completion. Something that handled 2 lenses could be very useful. 3 more so. 4 Nirvana (or was that 'hog heaven'? :-)).
Lens weight and size is obviously an issue. Ability to accommodate a range of sizes and mounts is necessary. Competency at grip, rotate, move, realign, reinsert both initially and at all times is essential.
What could be done:
Given the responses so far in comments and answer :-) :
I estimate that for a bayonet lens system, such as the Minolta A mount that I am most familiar with, I (personally) could design a lens changer that would swap between two small to medium size lenses in about 1 second. For larger lenses or to reduce cost - maybe 2 seconds. The technology to do this easily has existed for decades, to do it with some effort has been possible for many decades, and to do it 'if one must' for over a century. Using modern stepper motors and brushless DC motors, rotational and linear sensors (and (if one must) pneumatics or hydraulics)) would make doing it just a matter of doing it. Where are they?
A unit need not be essentially any larger than a lens bag made to accommodate the lenses concerned. The camera is inserted lens down into an open aperture and pressed home. The camera is gripped for a second or so and then a release light lights and the camera is withdrawn with the other lens in place. Dust and contamination incursion could be very low. Weight penalty is liable to be moderate - say less than 50% more than combined lens weight and maybe less. Power by eg LiIon battery pack - about as energy dense as is available battery wise.
If desired, when not in use a camera could be carried inserted in the changer so it can be withdrawn when required with the desired lens fitted.
Would it sell?
What would people pay for this capability?