This is the most frequently asked question we get online. Choosing the perfect interval is an essential task for creating beautiful time-lapse videos. But it’s not a trivial question, and there is no simple answer, because there is no “universal right interval”. Nevertheless, after reading this article, choosing the right interval should be a walk in the park.
What is an interval?
Let’s start right at the beginning and define what “time-lapse interval” means. The amount of time between each shot is called the interval. The interval can vary from less than one second up to days, depending on the subject of the shot.
To produce a time lapse, you shoot a photo, wait a couple of seconds, shoot another photo, wait the same number of seconds before you take another photo, and so on and so on until you’ve got a reasonable number of pictures, which you’ll combine to a video file in post-production.
Read more on this topic in “6 steps to shoot your first basic time lapse“.
Interval vs shutter speed
The interval is often confused with the shutter speed. So, let’s be clear that these are two completely different things. If you recall from our previous article “Manual mode for beginners“:
The shutter speed is the length of time you allow light to strike the sensor.
The interval is measured from starting point to starting point of each shot. As a result, your interval must always be longer than your shutter speed. Be aware that your camera needs some extra time after each shot to process the image and store it properly onto your SD card.
How to choose the right interval
There are two different approaches to find the right interval for your time-lapse shot:
- You know the look and feel you would like to accomplish and therefore choose the interval to bring that look and feel across (recommended)
- Or you know the length of the subject or event that you’re shooting and the length of the final video clip you would like to get out of it
Look and feel
The typical photographer uses three basic tools to determine the look and feel of their creations. The good news is that time-lapse photographers have got one more tool to use. And it’s called – you guessed it – the interval. But this also adds another parameter you need to pay attention to, which makes things slightly more complicated.
The interval controls the smoothness of your time-lapse video.
For example, take a look at fast-moving traffic in your time-lapse shot. Choosing an interval of 2 seconds will leave you with a much smoother outcome than using a 10-second interval.
Let’s assume a red car passing your camera needs 20 seconds to drive through your field of view. An interval of 2 seconds gives you 10 images of the car passing, while an interval of 10 seconds leaves you with just 2.
With 10 images of the car continuously moving from right to left, there’s a good chance that your brain will recognise this as the same car. With only 2 images of the car, it might pop up at the right edge of your frame and suddenly at the left. This is too little information for your brain to recognise that this is the same car moving from right to left.
However, there are times when you want exactly this effect. For example, you want to emphasise the traffic chaos at this crossing. Then this is the right setting for you.
Knowing the length of the final product
This is pure maths. But no worries, it’s very simple. In addition, there are several good apps out there to do the maths for you, including Photopills.
In case you don’t want to depend on some app (and also for your understanding), we recommend learning how to calculate the right interval by yourself. We recommend using this method of choosing the perfect interval whenever you know the duration of the event you would like to record. Choose a frame rate (read about that here) and the length of the final video clip. Here’s an example:
I want to shoot the sunset from 7 p.m. until 9 p.m., which is 2 hours. I want to get a 10-second time-lapse video out of it. As the frame rate, I choose 25 frames per second. I will compress 2 hours into 10 seconds.
2 hours equals 7,200 seconds. 2(hr) X 60(min) X 60(sec) = 7,200
For a 10-second video I will need 250 pictures. 10(sec) X 25(fps) = 250
Next, I simply have to divide the recording time in seconds (7,200) by the number of pictures (250) I need to get my desired length: 7,200(sec) / 250(pictures) = 28.8
This results in an interval of 28.8 seconds. We recommend always rounding down, because this will give you slightly more pictures in the end. And it’s definitely better to have some extra frames than missing some in post-production. So, let’s use 28 seconds as the interval for our time-lapse clip.
If you want to make sure you’ve got all of this, we recommend running some of these imaginary calculations on paper and checking your results with this online calculator.
Every subject is different
Above all, keep in mind that every subject is different. Traffic moves way faster than the sun. So, for showing the sun moving I’d rather choose an interval of 20-30 seconds to see some progress, whereas an interval of 4 seconds is better suited for traffic.
To get a feeling for the speed of things and choosing the perfect interval, you will need a bit of practice. The best advice we can give you is to just go out, shoot and experiment with all different camera settings and intervals. Evaluate your outcome and try again. And again. This is the only way for you to find your own style.