Complete Guide to Filming A7s II or A7r III Underwater
With underwater cases for GoPros and waterproof iPhones, the common idea is that you can take a camera anywhere with ease. In reality, taking a professional camera underwater is a daunting task. When you’re on the shoot submerged in unfamiliar territory, everything goes out the window.
On “Nomad”, a film I DP’d back in 2016, we took a Sony A7s into the ocean 25 miles off the coast of California. We had no place to research issues that arose. It was literally sink or swim.
Cameras don’t come with an instruction guide on filming underwater. So here’s a detailed guide on operating beautifully and effectively in any body of water.
Essentials - Gear
Gear is the essential starting point for diving into underwater filming. We used a Meikenon underwater rig, with the Sony FE 28-70mm f/3.5-5.6 OSS Lens rented from Borrow Lenses. The case is designed for this specific lens but other lenses will work as well. Other lenses worked but having the optical zoom feature was helpful with the A7s Mk I because the lack of 4k, so cropping in on footage will result in quality loss. But the same principles apply with the Mk. II & the entire A7 series. Whichever lens you decide to use, activate autofocus or get a metabones adapter that can.
In terms of personal gear, scuba goggles and a snorkel are must-haves. Scuba tank would be optimal, but it also requires scuba training & certification. The final piece of essential equipment: a surf strap. You will velcro this to your arm in order to keep the camera safe. The velcro also allows you to easily unstrap if you're ever in a dangerous situation.
Before The Dive
Before you enter the water, it’s necessary to adjust the settings and prepare for submersion. First step is the aperture. You want to set the F-stop where you get a smooth depth of field but also where autofocus doesn’t work too hard. We cruised around f/5.6 to f/8. Adjust ISO to properly expose for this. Now keep in mind it’ll be pretty overexposed above water.
Despotting Lens & Sensor
Since the aperture is stopped down, any lens spots on the sensor will be more visible. This is due to a significant design flaw in the A7s that leaves it more prone to sensor spots than comparable cameras. To avoid this, clean the sensor thoroughly before getting near the water. Follow this guide to cleaning process.
Sensor brushes are particularly effective with cleaning dusty sensors. A colleague at a rental house said that he uses brushes for Sony sensors 95% of the time. Once you cleaned the sensor, point it at the sky at a closed aperture such as f16 to confirm the sensor is clear of spots. Any spots will be highlighted by the sky.
Most cameras, including the A7 series, have the feature to shoot in 60+fps. By shooting in 60fps and slowing down the footage to 23.976, the footage will be 250% smoother and clear of jitters while also making the subject movement far less erratic. Slow motion footage underwater looks very natural. Make sure the shutter speed correlates with 60fps at 1/120. If shooting in 120fps, set the shutter speed at 1/240.
During submersion, light metering is crucial. Utilize the M.M. +/- meter on the bottom center of display. Focus on the metering because you will not be able to see the screen very well. Anticipating the framing is going to be a common occurrence. But playing with different framing can allow you to construct a scene, so don’t hesitate to get various close-ups and wide shots.
Interpret the footage in your post-production program as 23.976fps. This will give it a smooth 250% reduction in speed and clear jitters, while also making subject movement far less erratic.
Underwater is whole other world. It’s almost an alien environment and you have to approach it as such. Things will not go as planned. There will be moments that your aperture is too closed, spots somehow found their way onto the footage, or an enormous ocean riptide hits and drags you about 100 meters away from the subject. All of these happened to us, so take the precautions to ensure that you’re fully prepared to take on any body of water.