It is not a mystery that even the new Mark IV version has issues with custom white balance.
The ergonomics have not changed and you need to go into photo mode to set custom white balance but generally underwater results are poor. Using filters is therefore a necessity also on the new 4K version.
RX100 Mark IV Video Behavior
The RX100 offers now a 4K 100 mbps mode and can use picture profiles.
I have used a modified version of PP6 that use the cine2 gamma curve, I have however changed the colour to the Pro mode and changed a number of other settings in my last video in Puerto Galera.
The water was green and murky but this gives you an idea of what you can get.
Filter Options and Wide Angle
Although the Nauticam WWL-1 is the best lens for the RX100 it does not take filters and therefore is not adequate for video.
In this review clip you can see the options available on the market.
In terms of wide angle you have two options for 4K:
- Inon UWL-H100
- Inon UWL-100
Both lenses work fine in 4K however the older UWL-100 achromat does vignette in photo mode.
The UWL-H100 offers a very wide field of view also in HD mode with no vignette and accepts the mangrove/deeproof filter.
This filters is loaded with magenta so I suggest adjusting the tint in the auto white balance mode to +2 green.
The UWL-100 works fine in 4K and is wider than the UWL-H100 however has only the M67 mount. If you have one of those lenses you can use the Ikelite 6442 filter. This filter required you to remove the rubber ring on the lens and does work quite well except has a yellow cast to it you can reduce by changing the tint to +2 blue and increasing also magenta to +1.
For flexibility purposes probably the UWL-H100 is better as it takes the bayonet but the UWL-100 is really wide and has a little less fringing. Some people do like the UR/PRO filters better.
I hope you find this post useful and good luck with getting the best colours from your Sony RX100 Mark IV