2x extender. Fotodiox or viltrox or save

Rahto wrote:

My experience with third party converters seems to be every time I upgrade to a new Canon body the converter is no longer compatible and that has not been the case the Canon converters.

The DGX Kenkos seem to be incompatible with newer cameras, but the Kenko Pro 300 DG 1.4 (not DGX) that I bought 17 or so years ago still works with every lens I've tried it with on the R5.  As a second, hidden TC behind another one, however, it tends to cause incompatibilities.

I suspect that what Canon is doing is trying to determine how many items are connected to the mount and throttling power to the mount to a level which should be just enough, but if a hidden TC that doesn't report is in the chain, it may load the power supply so that the lens no longer operates.  I never had this problem with DSLR mode on my DSLRs, or with live view up to the 7D2, but my 90D in Live View has some of the same issues.

The combinations that work or fail is hard to guess, though.  For example, with my 400/4DO II, I can put the Canon 2xIII on it and put a Kenko 3x DG behind it, and it focuses and IS works, at f/24.  If I use just that 3x, though, it doesn't work!  It doesn't even work if I tape the TC pins!  It also doesn't work if I put the Kenko Pro 300 DG 1.4x behind the 2xIII; the IS just bangs, and if I turn the IS off on the lens, it works for a few shots and then gives a communication error.  None of this follows any simple logical pattern.