Thanks for that - my thinking was that a lever type would offer the reassurance of knowing it had locked in
The problem with lever types is that arca swiss plates are not standardized so the clamp can be too tight or too loose. You can get lever clamps that are adjustable, but a lot of times that just makes it a "quicker releasing screw clamp" because the adjustment is the screw tightened opposing side. There are some where the lever side is adjustable for width/clamping force, with some of those the adjustment is pretty coarse (half turn minimum).
Not a lot of help, but I haven't had an issue with the screw type (good quality Kirk or Acratech and branded, but cheapish ones from Amazon) but I have had problems with clamp designs (branded but low price, not the cheapest, from Amazon) for the reasons @sk66 said. Both had locks on the actual clamp, so the clamp part was solid, it was the adjustment that was the problem.
novoflex.co.uk
Unfortunately, it isn't just the "cheapo camera brackets" that might have a problem.
I didn't know that Graham, I must be lucky because all my plates bar a couple (various sources) fit my lever clamps OK (I have 3 on different Tripods).
I have only had personal experience of cheap plates not clamping properly, but it crops up every so often.
Thanks for that. The near miss was totally operator error; it was early in the morning so I wasn't fully alert and I "thought" I had tightened the clamp fully. I went to move my tripod slightly and in that slow motion moment the camera slid out. Fortunately I managed to catch it before a potentially expensive connection with the ground !I am not sure how the near miss might have happened?
FWIW
I have used for some time a Wimberley C-12 scree version clamp and chose, in part, at the time for it's chunky screw knob compared to alternatives that in effect have a milled finish to the knob grip.
Now, for what ever reason when clamped tight I sometimes struggled to undo it. I then read on a forum (cannot recall which one?) a post by someone who asked the maker about increasing the grip by replacing the size of the knob.
They were kind enough to send me two off of their experimental production, 3D printed, knobs and they were great.
Latterly, (IIRC mid to late last year) I too was looking for a lever clamp and bought the Leofoto LR-70. I checked that my Wimberley &Surui plates 'played nicely' in regard to clamping pressure/tightness.
Now, though I would have preferred one with an auto-lock in the closed position, I think the Leofoto one with it's (as far as I can tell) good detente past TDC of the cam action plus it's half open position that when combined with a plate that has its 'slide stop screws' in situ should be as "safe" as one could be.
HTH
PS as mentioned by others above, you need to buy your plates wisely. IMO any of the good(?) manufacturers should be making them to tight tolerances........perhaps the same cannot be said for the budget brands???
Caveat emptor in all matters, especially when buying on a budget. Personally I would not trust my £1000's of camera gear to something that cost, say, £30
What is the saying 'penny wise, pound foolish' ???
That looks very good. The tension screw seems a good idea in light of the earlier posts regarding non standard plates sizes