Many suppliers – ourselves included – advertise quick releases and plates as being ‘Arca compatible’, but what does this mean?
The Arca Swiss design offers strength with simplicity of operation, being a plate (of varying length) with a standard profile incorporating a 45° dovetail which is held in clamp usually tightened by a side screw. It also allows the plate to be slid along the clamp without fully unlocking it, so is very useful when balancing heavy equipment.
However, Arca Swiss has never published a technical specification for the design, so any other makes are just copies, and inevitably small differences can occur, hence what should be compatible turns out not to be. It’s for this reason that Arca Swiss, and many other high quality brands, will only guarantee performance when their plates are used with their clamps.
However, in practice, we’ve found (from the makes we stock) that most plates will work with most clamps, but we have experienced several instances, usually involving L brackets for some reason, of incompatibility. And we can’t even say that ‘Maker A won’t work with Maker B’, as it can vary from product to product within the brands. The reasons usually involve either a slightly different plate profile or insufficient movement or tolerance built into the clamp – especially common with lever-type lock versions.
Many of the Chinese and Pacific Rim manufacturers, e.g. Sirui, Markins, and Sunwayfoto have copied the original Arca Swiss design, as used on the B1 ball head for example. This has a platform of varying depth, under which there is a single 45° dovetail.
A group of US manufacturers, including RRS, Wimberley, Kirk, Acratech and Jobu, has sought to establish a North American standard. The North American version has a V-shape 90° profile and standard lip depth which will allow the plate to be installed either way up. (Note that, in response to this, Novoflex changed the design of their QPL-SLIM plates to be compatible with the US standard: see the diagram below.)
Parallel to the above, a group of German brands, comprising Berlebach, Cullmann, FLM, Linhof and Novoflex, established the UniQ/C standard to guarantee cross-compatibility between their products, and other makers have subsequently adopted this: a list of makes and products can be found here The Novoflex standard QPL plates adhere to this pattern.
So if you really want to be sure, we’d always recommend sticking with the same brand or standard, or if not, test your plate in a safe environment to make sure it clamps properly with adequate overlap of the dovetail. If they don't fit tightly, don't use it.
But if you’re thinking of buying a particular plate or clamp ‘blind’, do give us a call – if we have the items on the shelf we’ll be happy to test them before you commit.