What interval should I use for a canal boat timelapse?
Asked 4/2/2019
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I’m planning a timelapse during a canal boat trip and only get one chance to capture it. I know the boat’s approximate speed and want the final video to feel natural rather than too fast or too slow. How can I estimate a good shooting interval based on boat speed, playback frame rate, and total trip length? I’ll likely keep the camera fixed if possible.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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If you play the video at 30 frames/s, taking one picture/second is a 30x speedup. If your boat sails at 3mph, the time lapse at one picture/second will be a simulated 90mph. How much of a road can you see driving a car at that speed?
Taking the problem by the other end, figure out your "cruise" speed when in a car, divide by the boat speed. This is your "acceptable speedup". This speedup is your timelapse image interval multiplied by the framerate of the playback (20-30fps).
Of course if you want to shoot the whole cruise (say 3 hours=10000s) and make that a 10mn video (600 seconds) then you have to take 12000 pictures, roughly one picture/second but it can be a bit fast.
Keep in mind that the fjord cruise is taken from high above water in a wide fjord, so the feel of the speed is much less and you can use greater speedup factors. This would also be true if you drive your car in a desert (vs. in a forest or downtown). But picturesque waterways are seldom in a very open landscape.
Last, shooting too fast may induce more wear in the camera, and require more storage(*) and/or battery capacity but you can drop frames to slow down the final video. If you are too slow when taking the pictures, you can't fix it later.
(*) Of course for a time lapse, you may set your camera to a lower resolution or lesser JPEG quality.
Originally by user75947. Source · Licensed CC BY-SA 4.0
user75947
7y ago
0
Generated from our catalog & community — verify before relying on it.
A practical way to choose the interval is to work backward from the final look you want.
At 30 fps, shooting 1 frame every 1 second gives a 30× speed-up. So if the boat moves at 3 mph, the video will feel like about 90 mph motion. In general:
speed-up = interval × playback fps
So if you decide what “comfortable” apparent speed should feel like, divide that by the boat speed to get the needed speed-up, then divide again by your playback frame rate to get the interval.
You can also calculate from total duration:
interval = trip length in seconds / total frames needed
total frames needed = final video length × playback fps
Example: 3 hours (10,800 s) edited to 10 minutes at 20 fps needs 12,000 frames, or about 1 shot every 0.9 seconds.
A fixed camera on a tripod will usually give the smoothest result. Keep the interval consistent with an intervalometer or built-in interval timer. Also remember that perceived speed depends a lot on foreground/background distance: nearby objects will look much faster than distant scenery, so test wider views if you want a calmer-looking result.
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