With on-sensor phase detection autofocus systems already achieving speeds of 0.08 sec. (Fuji X-T1) and 0.06 sec. (Sony A-6000), and consumers demanding better video AF, there's a high liklihood that dSLRs may switch to on-sensor PDAF and mirrors will become obsolete in the near future. Then the "Mirror Forum" will become awfully quiet!
Since I've gotten good results with my Equinox and Ikelite underwater filters, the next logical step is to test the GoPro 3+ Black with both to determine if the overly megenta cast in the shadow areas was caused by the Polar Pro filter or the new Hero 3+ color engine.
The GoPro 3+ Black, mounted on the NEX-5R, was recording video when the sample photo was taken. Underwater, the screen image on the NEX-5R with an Equinox red filter was almost identical to the scenery. The GoPro 3+ / Polar Pro Red Filter setup produced decent kelp color, but the shadow areas all turned violet. Reducing magenta in the shadow areas turns the kelp green. I'll have to figure out how to properly correct the GoPro videos and photos. Fortunately, NEX-5R was my main camera not the GoPro.
The kelp footage in this Polar Pro / Hero 2 promotional video look good, but on my Hero 3+ Black the results were quite different. Perhaps the color model used by Hero 3+ Black had changed so much that it's no longer compatible with the Polar Pro Red filter.