Two days ago, I reviewed the SmallRig plate for the Sony a7III/a7RIII/a9 cameras. I found that the shoe that engages the tripod head clamp was wider than the Really Right Stuff (RRS) plates, making engagement with the cam-lock quick-release RRS clamps very tight. Today, I measured the dimensions of the bottom of a group of RRS and SmallRig plates. Here’s what I got:
It’s pretty clear that the SmallRig design center is greater than that of RRS.
I did not measure the angle and inner dimension of the plates, because I don’t have the tools to do that.
Some interesting reading on the Arca-Swiss “standard”:
http://www.jobu-design.com/Arca-Swiss-is-NOT-a-standard-time-for-a-change_b_8.html
https://www.tripodhead.com/products/product-details2.cfm?product=arca-swiss-geometry
http://www.afximages.com/stuff/arca-plates-xref.html
http://www.reallyrightstuff.com/patents
I have given up using the RSS Quick Release clamps and use a screw clamp instead. Too many variations of sizes, especially if you need to mix brands or use specialist devices such as focus rails, etc…
The difference you see there is just how much of a round they put on the edge of the dovetail. RRS rounds theirs pretty aggressively.
Though, as you say, you have no means of measuring it, you need to measure the distance between the lines where plane of the dovetail faces and the bottom of the plate meet.
If the difference were truly 1.5 millimeters as you measured, the lever lock would have no hope of closing.
One way to measure the dovetail is to use two dowel pins. The pins should have a large enough diameter that they touch the dovetails about halfway up the slope.
Place the dowel pins and the dovetail on a flat surface, and measure across the pins. This will allow you to measure the width of the dovetail at a consistent height from the bottom. (The same method can be used to measure the width of the inside of the female dovetail, depending on how the clearance at the bottom was machined.)
With two sets of dowel pins of different diameters you can measure the angle of the dovetails too.
There could still be differences in the amount of clearance left in the height of the dovetail, though.
Great idea, Frans!
Jim, RRS has a mechanical spec for their dovetail standard. 38.1mm sounds like it’s exactly what RRS specifies, or 1.5 inches in their spec’s units.
See here: http://www.reallyrightstuff.com/patents
Thanks for the information, Andre. I’ll include that link in the body of the post.
Personally, I use a clamp that has both a screw and a lever. It allows me to use any mount, small variations don’t matter. Once you use the screw to adjust to your mount, you can then use the lever for quick attachment and release.
I just bought a smallrig plate for my sony a7iii. I tried it to an alca-swiss compatible manfrotto head but it didn’t fit at all! I mean at all! I tried to squeeze the plate into the ball head with no good result. Both plates from manfrotto and joby work well with the ball head though. I guess I should change the ball head because of the plate?
other than that, it feels and weighs good with the camera.
I had the same problem with the SmallRig L plate for my Panasonic G9; the plate was too wide. Actually, they designed the plate with only one side cut out where it slides onto the ball head clamp. I informed the mfr about this defect, and they only said to return it if I didn’t like it. Rather than waste postage on shipping it back, I had a local machine shop cut out the other side. My advice is to spend the extra money and buy the RRS L plates.
I have several Chinese ‘Arca Swiss style’ plates and clamps of various sorts and brands. The dimensions of the dovetails differ, in realtive terms, quite a lot. In one the 45deg face of the plate’s dovetail is very low relative to the base, so low in fact that the plate will only lock in the clamp it came with.
What is most disconcerting is that the centre line of the plate often does not correspond to the centre line of the the clamp. This is even the case with a 360 deg panorama head where I would have thought this was one of the design necessities, I have corrected for the latter with a cross slide but it would be better if I didn’t have too
Where a plate will not fit into a screw lock type clamp if you can get to the end of the clamp’s main screw you may be able to loosen an axial retaining screw that screws into the clamp screw’s stud,. Make sure the screw driver is a good fit and pressed and held into the screw with appreciable force as it is likely that large amounts of screw locking liquid have been used to hold the retaining screw. Once the retaining screw is out or, if very stiff, backed off a bit the plate should drop in.
I purchased a used RRS quick release and some of my plates didn’t tighten up in the clamp. I ended up reselling it. Now I only use the screw clamp that came with my Induro tripod head. Be careful with RRS clamps. RRS said they are made for only the RRS plates.
Little late of a reply but since this popped up again. all the smallrig arca products are now designed to allow for both ‘specs’ to work including the new version of the l-bracket discussed here. The 2122v2 was done as a production update and been on sale for many months and should work fine. Also newer ones for 2236 and the now new model for the a7R4… (2417) and the upcoming pro version for that one.
Pretty impressive measuring, to one micron. Would you care to share with us your measuring technique?
Using an electronic micrometer with micron readout and averaging several readings. However, all those figures to the right of the decimal point are not significant.