Tag Archives: Underwater Video

Sony RX100 – Tips for UW Video Part 2 – Rear Dial Buttons

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.

Sony RX100 – Tips for UW Video Part 1- File Formats

When the new SONY DSC-RX100 was released early June many people were really excited as this camera featured a 1″ sensor at its heart.

Scott at Underwater Photography guide posted a raving review from which I was left salivating

Later on backscatter selected the RX100 as the best advanced camera of the year read more here however one statement left me concerned in the Pro and Cons section: No way to execute custom white balance in movie mode, must jump to photo mode

This sounded quite uneventful considering that we are almost used to one push custom white balance on most mid level compacts.

Maybe those guys looked at the Sony entirely from a still perspective and did not make much of the features or lack of thereof that this Sony has, anyway I have now bought the camera itself and I am facing a few issues and dilemmas.

Let’s take a close look at those one by one and start this issue with…


SONY has decided to adopt the new high specs AVCHD formats for this camera, I will from now on refer to 50p or 50i to indicate 50 progressive or 50 interlaced frames as this is the PAL standard. This would be 60p or 60i for NTSC US and Japanese users.

The AVCHD format had initially a 1080/50i and a 1080/24p format and a bunch of lower resolution formats, later on a 1080/50p format has been added with an increased bit-rate of 28 Mbps instead of the original 24.

Now you would normally assume that Sony would have chosen to support all those formats and instead has decided just for the 1080/50i and 1080/50p. The universal 1080/24p format that is compatible with both PAL and NTSC is not supported on the RX100. Why has Sony made this decision is a mystery.

The make things worse today interlaced display do not exist anymore and most of the non linear video editor convert interlaced footage in progressive otherwise you can’t actually edit the clips. Not only that very few software programs actually accept the new 1080/50p format, with the notable exception of Sony software that even at low level supports those formats. Adobe premier is another one, but the whole set of Apple software including iMovie and Final Cut Pro don’t know what to do with those files. Let alone the fact that no devices except powerful computers can actually play those files well.

The RX100 offers an MP4 format at 1440×1080 rectangular pixels with a 16:9 aspect ratio as a reminiscence of HDV. This format is however easily digestible by the majority of NLE on the market. So we would feel rather tempted to use it.

The question is how do we set our RX100 to capture underwater video?

The answer is actually at the highest possible setting that is 1080/50p. There are several reasons for this.

  1. The human eye is very sensitive to resolution. So the MP4 1440×1080 format goes out of the window
  2. We can still change the frame rate in editing phase to make the file a more normal 1080/25p
  3. There is not a huge difference in memory card use between the 24 Mbps of the highest interlaced mode and the 1080/50p
  4. It is easier to edit progressive frames without conversion
  5. Progressive footage does not introduce artifacts as  interlaced does

On a negative note the fact that we are saving AVCHD streams means goodbye back ups on our tablets or mobiles so plenty of memory cards with us during our trips.

The next challenge will be to import the AVCHD streams into our movie editor. As mentioned earlier the 1080/50p format is not recognized by many entry level programs so some will not even see those files.

Other programs will try and convert it, this option has to be disabled and the files imported as they are without any changes to preserve quality.

So what do we do if our software refuses to process the 1080/50p files in our AVCHD streams?

A number of help tools come handy unfortunately the freeware one are mostly on windows and I have not managed to produce anything that works yet with Wine for Mac. On Mac there are two tools iVI that costs $9.99 and ClipWrap more expensive both functional and will produce an M4V or MOV that can be processed with iMovie or other tools that would have previously rejected the file you go figure!!!