Normal TV cameras film at 25 frames per second. High speed cameras operate at much higher rates – up to thousands of frames per second – and when this is played back at 25 frames per second, you get a highly detailed slow motion sequence.
This effect was used in Planet Earth in 2009 to show a great white shark jumping out of the sea to snatch a grey seal. This was filmed at 1000fps, which made the action appear 40 times slower than in reality.
These are his tips on filming at frame rates.
Get to know the kit
There are some film and tape based cameras which can shoot at increased frame rates. However, most high speed filming is done on file based cameras which work like DSLRs, shooting multiple JPG images which can then be stitched together on an edit timeline.
Because these cameras are file based you need a lot of extra kit as well as the camera body. This will include a laptop for downloading, lots of hard drive storage space and batteries to power it all. You’re also likely to need a much heavier and longer lens than you would to film the same action on a standard camera. As with any kit, make sure you check it over and experiment with it before you’re under pressure on a shoot.
"It can make a split second action an incredibly beautiful piece of television."– Simon Blakeney
Get close to the action
High speed cameras don’t have the same magnification as normal tv cameras. You may need to get much closer to your subject to achieve the same image size in your frame. Simon uses a clip from Life: Fish, broadcast in 2009 to illustrate the problems of filming at high speed. The team had planned to film flying fish from a large boat. However, they quickly found that they couldn’t get the boat close enough to the action. To get their shots they decamped into a much smaller dinghy, which was much lower in the water. This enabled them to get closer to the fish. But because they were also much closer to the water, they had to waterproof their gear with plastic bags.
Experiment with frame rate
Getting the right frame rate is a matter of trial and error and you’re unlikely to get it right the first time. If you shoot something at 2000 frames per second that lasts a second, when you play it back at normal speed it will last 80 seconds. You’re unlikely to be able to use a shot of this length in your edit. So it’s worth experimenting. The temptation is to crank the camera up to its maximum frame rate, but this may not suit the action you’re filming.
Factor in download time
Download time is a major factor with any file based camera. While filming the bait balls for Life, the cameraman could only take four shots, each lasting three seconds, before the camera cards filled up and had to be offloaded. Each bait ball normally lasted around 20 minutes before the fish disappeared. It routinely took longer than this to pull the images off the cards. As a result it took more than a month of filming to complete the finished sequence.