Originally posted by Not a Number
It's doesn't look like a Rioch problem to me. Rather MTP (an Android IOS protocol) not being natively supported by Apple/Mac OS. Probably a licensing issue, Android IOS being a rival of Apple/Mac OS.
Just do a Web search on "MTP transfer Mac" and you'll see there is no native support in the Mac OS. Apps like IPhoto will support MTP though. The most common solution is to use Android file transfer app that @clackers linked above.
There
IS a Ricoh problem here. Page 110 of the GR3 manual makes
NO mention that the camera may not be recognized by a Mac. The memo at the bottom of the page refers to the system requirements on page 152, which indicate that the last 5 Mac OS versions, starting with the current (Mojave, 10.14), can make a USB connection with the camera. No mention is made that MTP transfer protocol must be supported.
I found this confusing for far too long, and this thread got it straightened out for me. I got the Android file transfer app to get the transfer to work, but Ricoh should have this information in their GR3 manual.
So, at the least, this is a documentation error - a lack of required information.
Personally, I would prefer that the GR3 support the same USB protocol that all my Pentax cameras support, even if a USB protocol selection must be done in the GR3 menus.
By the way, the GR3 is a terrific walkaround camera. So many times, a DSLR is just not needed, and the GR3 fits in my pocket. Lousy battery life though, if you want to shoot everything in sight. A few lightweight batteries fix that problem, though. Still fits in my pocket.