The successor to the Canon EOS R6 Mark II, which is an absolute pillar of the R system, the Mark III has long been rumored to feature a stacked sensor similar to that of the EOS R3. However ...
If you have a Sandisk SD card in your Canon EOS R5 II, you may want to check that it's compatible. Canon recently put out a warning, reported by The Digital Picture, that "certain SanDisk Extreme ...