Hello, I have just been doing some tests with the 12-50 port and gear and though this info would be of interest.
"Regular zoom" mode. The operation of the power zoom is excellent. The zoom knob on the housing controls the zoom as you twist it against the spring-loaded power zoom ring on the lens. For most of the twist, you are in "slow zoom" mode (better for video), but at the very end of the twist, the lens jumps to "fast zoom" mode (better for photos). If you don't twist it all the way, it is easy to assume that you only have access to "slow zoom" but that is not the case. The twist to fast zoom takes only a second. Close focus at the wide end is under one foot. This is a great solution for general scenics. Maybe it is possible to get CFWA with a diopter, but I do not have one to try this with.
"Macro" mode. This is where it gets really amazing. The switch is instantaneous and, no matter where you were in the zoom range, the lens jumps to 43mm and the farthest focus possible in macro mode (one or two feet from the subject). You move closer to get higher magnification. I can fill the frame with a SD memory card. Measuring the card, it is 25x36mm. In 35mm terms this is "true macro" because it is 1:1 magnification. Thus, this lens magnification equals what is still, today, the maximum magnification of 35mm full frame macro lenses.
The working distance from the front of the port at this magnification is 2 inches. So, with a diopter, it might be possible to get even higher magnification although you will be getting very close. Not sure if it would work as I do not have a diopter.
I had ordered the flip adapter for this port, but the high magnification of the lens and the close working distance caused me to cancel that order. It is just not needed.
These tests were on land as I have not gotten out to dive with it yet, but I can't wait!!
For Roger C above, I have shot in optical TTL with 2 YS-D1s using the 12-50 in macro mode at 2" from the subject, and the TTL worked fine. Manual exposure mode at 1/250 shutter speed, but TTL exposure mode for the flash (set camera flash to "fill" and strobes to TTL). Also, the D1s give nice ratio lighting control even in TTL for creative shadows and textures even at that close distance.