what’s the difference in filming a video and speeding it up vs time lapse video?
In: 8
Time lapse videos typically take many fewer pictures in their filming in order to not have to store an 8hour movie for a 5 minute video
They might only take one frame every few seconds for example instead of taking dozens of frames per second
Recording at normal speed and then speeding it up takes a lot more storage. Time lapse takes an individual image at set intervals. So while it takes an image every 10 minutes you have 144 frames per day which is about 3 seconds at normal speed. Recording at 30 frames per second for a day gives you 2,592,000 frames and speeding it up to play in 3 seconds would would be a blur unless you threw away a bunch of frames.
That depends on how you do it.
“Filming a video” is a very incomplete description. How many frames per second do you capture? How long do you expose each frame?
“Speeding it up” also is incomplete. Do you speed it up by showing more frames in the same timespan, or by dropping frames?
With the right answers to those two questions, there is no difference.
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But that’s boring. So, let’s say you take a video at 60 fps and expose it at 180° (i.e. each frame for 1/120 second). To speed it up, you drop 59 out of every 60 frames.
The other guy makes a time-lapse video. He takes 1 frame every second and also exposes it for one 120th of a second.
The result is completely identical, only that you have a couple of GB of data to delete that the other guy never took.
Another example:
You do the same, but the other guy changes his exposure to half a second.
The result is quite different. The other guy has produced something you can not get from your material by dropping frames. And visually the results look quite different, too. Yours looks like it’s sped up (because it is), but his looks like it was taken at normal speed and everything moves very quickly.
The difference is motion blur. The sped-up footage had normal motion blur before it was sped-up, but after that, it only has 1/60th of it. That’s as good as having none at all. However, the timelapse footage has the same amount of motion blur it would have, if it was normal video of fast objects.
Third example:
You take the same video, but speed it up by showing it at 600 fps. You now have an ultra-high framerate video that looks very eery because it’s abnormally smooth. No matter who looks at it, there’s not the smallest hint of it being composed of frames left. The effect you get is that of a window instead of a monitor. Even worse than The Hobbit.
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In summary, the difference is whatever you make it. You can get the same results or vastly different result, depending on the parameters you film with. After all, a time-lapse video is just a normal video that was taken with low fps and played at normal fps.
Efficiency.
If you want to take footage to cover a 12 hour period, leaving a camera running normally for a full 12 hours is just impractical – you would need to be babysitting your camera so that you could swap out memory cards and batteries as they fill and empty respectively, and then would be left with a vast amount of data that you need to store and edit into your final footage which means more hard drives, and more powerful computers will be required to deal with all of this.
After all of this, you will end up throwing away almost all of the data you have recorded – a 30 second long video at 30fps will take 900 frames worth of footage.
12 hours of recording at 30fps will create 1,296,000 frames worth of footage – you would be throwing away more than 99% of the footage you shot.
The answer to this is to use a time lapse. Instead of running the camera constantly, we can figure out that if we want to record 900 frames worth of footage over the course of 12 hours, we just need one frame every minute and fifteen seconds. So we can use some software to control our camera so that rather than running and recording constantly, it can go into a power saving mode while not actually recording.
Of course there is some leeway in what is practical – if you just want to speed up your footage x2 or x4, it may make sense to just record in full and edit later to give you more control.
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