Over a year ago I wrote a set of posts for the RX100 and some of the quirks of this wonderful little camera.
Steadyshot – aka Image Stabilizer
The RX100 has a specific Active mode for video not available when taking stills. I described the differences between those two modes in this post
Everyone is so obsessed of having the widest possible field of view that other more important considerations are completely missed out.
If you have ever shot a video with a GoPro underwater you know how bad is the quality of the image in the corners, this is because the flat port combined with the gopro lens create many optical aberrations.
Our RX100, especially the original Mark I, also has an issue in the corners, this is not just an underwater issue is also true on land. The lens on the camera has a lot of distortion and when corrections are applied to the image this effectively creates corner softness.
When we add a wide angle lens the image quality in the corners deteriorates further especially if the lens is flat creating a lot of chromatic aberrations that you can see in pictures with a blue or yellow halo around the edges.
Now the good news the Active steady shot mode crops the image of a factor of 1.15x getting rid of the majority of the corner softness.
There is of course a price to pay which is the loss of some of the angle of view. According to my calculation if you use an Inon UWL-H100 you start from more than the declared 100.8º more around 104º in fact. When the active mode is on this drops to around 95º. Remember all those values represent the largest incident angle that means the diagonal field of view.
A lens with 100º diagonal field of view means 90º horizontal. So after the active mode is engaged our horizontal field of view looks more like 84º which is equivalent to a 20mm lens. This is sufficient for most close wide angle shots and plenty for ambient light videos of large fish or wrecks. I generally suggest to keep the Active mode on, of course if you can be in a fixed position and hold the camera really steady you can also use the standard mode and obtain more field of view. There is a chance though that you will need to crop the extra field of view if you need to stabilize in the editing phase.
For macro shots without a tripod the steadyshot is a must and helps greatly. I do not even see a reason to take it off if you have a tripod as the RX100 does not have a particularly small capture area.
This brings the second subject: digital zoom, if you shoot pictures you avoid it as what you are doing is to crop the image, something you can do yourself in processing. In video though there is very little quality loss as we use just 2 megapixels of the 20 of the RX100 camera. In my test you can use digital zoom until the 2x multiplier is reached, this corresponds to 7.2x magnification and see no noticeable degradation in the image quality. The other benefit is that the depth of field is the same despite the magnification so you can save yourself stacking two diopters with all the difficulties that follow in terms of focus.
Digital zoom is always on in video mode and I recommend to use it with a single close up lens before embarking on dual diopters or a strong single diopter. Also take into account that with a single +6 diopter your working distance is around 4″ which is ideal for most critters except pygmy seahorse and bobtail squid or some shrimps.
In another post I have explained that getting hung up about light angle coverage is not really the only thing to consider, there is also luminous flux and quality of light. With my Sola 1200 I can cover something between 2 and 4 feet away with decent results further away is just back scatter. Generally this is ok for some close portrait work and close wide angle and of course not sufficient to cover part of a wreck or much larger subjects. You may decide not to bother at all with lights for wide angle and just render your deep wreck dives in black and white in this case consider that a pair of Sola Dive 800 at $399 are a high quality macro set up, function as dive light and provide some decent close wide angle portrait illumination. For macro shots you need much less than that, I set my fill light at minimum (300 lumens) and the main light at 2/3 which is 600 lumens, I can shoot at f/11 with this light intensity. You can see me shooting in the feature image.