The yearly refresh of the Sony RX100 brings us the mark IV and with it comes 4K video.

The sensor of the camera is still the same 1″ size of the RX100 but Sony has now added an XAVC codec at 100 mbps with 4K resolution as well as a lower 60 mbps mode that adds to the 50 mbps HD modes of the mark III.

So now we have two compact cameras that can record 4K video and the Panasonic DMC-LX100 is not alone.

Frankie Fok has a nice clip from Socorro with the LX100 as shown here

There is to date one only example with the Sony RX100 Mark IV and is not in the best environment but it gives an idea

So if you want to shoot 4K with a compact camera underwater which one should you choose, if any?

Panasonic DMC-LX100

The LX100 has some interesting characteristics, although the sensor is in fact the same of the GX7. The camera has a good sharp lens and as all Panasonic the video implementation includes an IPB codec for video that makes compression very efficient.

However the LX100 has a number of issues and challenges as well :

• No Auto ISO in manual mode
• No ND filter
• Short zoom range 24-75mm with multi-aspect sensor (26-81mm in 4K video mode)

The most serious problem of the LX100 is certainly its lens.

Nauticam released the housing early and for the first time it featured a port system.

To my horror the default port is rectangular, this creates a host of issues including the fact that you can’t easily add a close up lens in front without an expensive adapter.

The camera weights around 400 grams with battery and you need to add another 1.2 Kg for the housing for a total of 1.6 Kg more than some mirroless cameras such as the Panasonic GX7 or the Sony A5000.

You need around $2,000 to get the camera and the housing which is not exactly cheap for a camera that can’t do wide angle and you need something like the Nauticam CMC to achieve 32mm width in the frame however the diopter holder is $220 and other $320 for the CMC.

The port system has challenges too, for example the mini dome only allows for limited use of the zoom range and the short port locks the zoom completely.

Update: Nauticam has told me that the dome should work on the entire zoom range am waiting confirmation

The Sony RX100 mark IV has similar issues:

• A short lens 24-70mm that becomes 28-81mm in video
• The video codec has only predictive frames (as all Sony) and is less efficient than Panasonic
• 4K video is limited to 5 minutes before the camera auto shuts down

The RX100 has several other attractive features that the LX100 does not have:

• ND filter
• Auto ISO in manual
• Allows for external recorders
• Image profiles for video similar to professional equipment
• The housing does not have a port system

The issues at close range are the same of the LX100 and the RX100 requires similar solutions, but at least you have an M67 thread, what’s more important at 28mm you can use a normal Inon lens UWL-H100 to achieve a wide and rectilinear field of view and also a push on filter. Most likely filters are still a must due to Sony well known issue with custom white balance.

The smaller Sony sensor does mean worse performance at low ISO but having seen the LX100 results this seems to be an issue there as well.

The RX100 mark IV + Nauticam housing comes at similar cost but does not require additional ports. The rig is truly portable at around 1.1 Kg in total.

The 5 minutes limit is not an issue for underwater use although it is a limitation on land for sure.

I am not convinced that any of those two compacts are actually worth investing as both use the H264 video codec that is not designed for 4K. This generates all sorts of issues at low ISO as well as being really processor intensive to the point of over heating the sensor like it happens on the Sony.

If you really want to invest in a small rig for 4K underwater video my preference would be the RX100 mark IV but is very likely that personally I am going to stay on HD for another year