In this second post we will look at how to set the rear dial buttons to best suit underwater video.

The RX100 has got a whole load of settings and not the most user friendly menu structure so it is important to have the features you need at your fingertips when the moment comes.

There are 3 essential features that a camera needs to have for underwater video:

1. AF lock
2. Exposure Lock
3. Set custom white balance

Unfortunately as Backscatter noted in their review of the RX100 there is no possibility to set a custom white balance in any of the video modes, however in the next post I will guide you through the best available workaround that minimizes the chances of you getting completely lost in the menus…

It may be beneficial to understand first why those features are important so let’s have a look one by one.

AF Lock

Have you ever experienced being in a school of fish? Or looking at some frantic behavior in front of you or simply seeing glassfish swarming in front of your camera lens?

It will look something like this…

This is not a still picture but a snapshot of a clip taken at 1/125 sec shutter speed, the action was actually fairly fast.

This is the clip if you want to check it out,

this scene is in the first part of the movie and  has been shot with AF Lock on a Sanyo Xacti HD2000.

What would have happened without AF Lock? The camera would have been looking for focus and mistaking some of the fish coming close with the actual subject and as result the clip would have been unwatchable. So this makes focus lock very important for us in all situation where we operate in tripod mode with moving fish in front of the lens.

The RX100 does not offer AF Lock with a single push, and in video mode the choice is between tracking auto focus and manual focus. To emulate the AF Lock feature I follow this procedure:

1. Track my focus point with tracking AF
2. Switch to Manual Focus

Note that is not possible to simply cancel tracking AF to obtain AF lock as the contrast detection system will still wonder around the center of the frame.

This means that one of the rear dial buttons accessible in the menu settings 2 should be set to AF/MF Control Toggle that will allow us to quickly operate the steps above and move with one click from tracking AF into manual and effective locked focus.

Exposure Compensation

Another essential feature of video as we don’t want the camera to continuously adapt to the changing light conditions of the scene. To give an example let’s have a look at this picture:

This is a swim-through that is a common features of little caves or even wrecks. We don’t want the camera to compensate for the lack of light whilst we go through as that would increase the ISO and make the footage grainy, also the scene would get brighter and not reflect to the viewer the same experience we had.

Exposure lock avoids this situation so when we are at the beginning of the cave we lock exposure and the scene stays dark so that the end of the swim through gives a beautiful effect. Another example with this technique

So we should reserve another of the rear dial buttons to Exposure lock that on the menu system is called AEL Toggle

This is how my rear dial configuration looks in the Setting menu 2

Note that I left the center button to standard as that corresponds to tracking focus. That is required for the pseudo AF lock in conjunction with the Right button as discussed earlier in this post.