The Basics of Time Lapse Photography
Writer: Dylan Mackenzie
Have you ever wondered how people compress great lengths of time into a matter of seconds? How the apparent motion of the the Sun, Moon, and stars across the night sky are captured? How a busy city center moves in fast motion? How clouds move across the sky faster than we see in real life?
All of the above things you see while watching a movie, TV show, or video on the internet are created using a technique called time-lapse photography. Time-lapses are created by capturing a series of images called frames over a longer period of time than that human eye can perceive naturally. The frames that are captured are then played back at a speed that is fast enough so that your brain perceives the individual frames as a “moving” image.
Historically time-lapses were created using expensive movie cameras loaded with large magazines of film and connected to a separate device called an intervalometer. An intervalometer is a device which uses a clock to trigger an action at a set time such as capturing a frame on film then advancing the frame forward in order to capture the next frame. For example you would set the intervalometer to capture 1 frame every two seconds. You then would of had to develop the film and play it back on a projector at 24 frames per second. The end result of this would be a timelapse that compresses 48 seconds into one second of film.
Fortunately with today’s technology you don’t need expensive professional equipment but you do need to know a little bit of basic algebra in order to know how long your footage is going to be. As far as equipment goes all you need is a digital camera that is able to capture frames at set intervals and a sturdy tripod. In some cases your camera will have a built in intervalometer but in others you may need to buy a separate device that can cost anywhere from $50 USD and up.
In order to start making a time-lapse you need to ask yourself a few questions…
- What do you want to make a timelapse of?
- What will be the interval of time be between capturing your frames?
- How long do you want the resulting clip to be in seconds?
- What will your playback frame rate be?
- How many frames will it take to meet the time you alloted in question #3?
- How long will you have to sit by your camera in order to meet your total run time and frame count?
The first question will determine the interval of time that is needed to make your subject appear to move faster than the human eye can perceive it in real time? It is determined by how long it takes to photograph (Expose) the subject and how fast it moves across your frame (Interval). For anything that doesn’t involve manual shutter speed settings all you have to worry about is the apparent motion of the object across the frame. The first thing I believe you should start with is cotton ball shaped clouds moving across the sky.
The second question will come from what you’ve concluded from the first question. In the case of clouds from my experience you want a minimum of 1 photo every 2 seconds.
The third question will answer how long you want the resulting clip to be? In this case let’s say you want a 10 second clip.
The fourth question is what do you want your frame rate (In frames per second) to be when you play back your sequence of photos? You can either go for a higher frame rate which will equal faster and smoother motion at the expense of needing to capture more frames per second, or choose a lower frame rate which if too low can look like a choppy slow moving slideshow of individual images. Over 100 years of motion pictures has determined that 24 frames per second as the standard frame rate for motion picture films and is a great frame rate to start making timelapses with.
The fifth question will answer how many photographs it will take in order to meet the time you’ve allotted with the frame rate you’ve chosen? As mentioned above the higher your frame rate, the more photos you will need in order to make at least one second of footage. 24 frames per second is what I believe to the minimum frame rate to perceive motion with the fewest amount of photos required. So at 24 frames per second 24 frames equal one second and I want 10 seconds of footage to work with. I multiply 24 times 10 and get 240 frames or photos that need to be taken in order to meet the allotted time.
The sixth and final question will answer how long you need to sit by your camera in order to get the amount of footage you want when you speed it up? This is the part that requires a little bit of algebra. In order to calculate this you need to multiply your frame rate with your run time in order to to get the the number of images you need to capture. Then take the number of images you need to capture and multiply it by your frame interval. After this you will get the time in seconds it will take to record this in real time. To convert seconds into minutes you have divide by 60. Below is the breakdown of the math you will need to do if you want to change any parameters of this example.
Using the example from the 6 questions above, let’s say you want to make a 10 second time-lapse of clouds moving across the sky to be played back at 24 frames per second. You’ve decided to set your camera to take two images every second. How many minutes would you have to photograph the sky in order to get a 10 second clip? The equation for time lapse durations is seconds recording the event (SEC) divided by the recording interval in seconds (INT) is equal to the total number of frames (FRAMES) which are equal to the frames per second (FPS) multiplied by the clip length in seconds (TRT).
In the above example we already have the total run time (TRT=10 seconds of playback) of the clip to be played, the frames-per-second (FPS=24 frames per second), and the interval (INT= 2 seconds between each frame) in which the time lapse is to be recorded. What we are missing from this equation is the total number of frames (FRAMES) to be recorded in the allotted time and the number of seconds (SEC) it will take to record the time lapse in real time.
We start by multiplying the total run time of the clip which is 10 seconds with the frames per second which is 24 fps. The resulting number 240 frames (FRAMES). Then take 240 and multiply it by your interval of 2 seconds (INT) between each frame, the resulting number should be 480 seconds (SEC). We don’t think in seconds over 120 so let’s divide by 60 in order to get easier to digest minutes in which we end up with 8 minutes of photographing the sky. Check your math to make sure all 3 parts are equal to the number of frames you need to capture.
After you’ve calculated all of your parameters, you need to gather your materials in order to make a time-lapse, you will need a camera that is able to have it’s shutter actuated at set intervals and a sturdy tripod to keep the camera still. You start by setting up your camera on a tripod set up on level ground before framing your camera. In the case of shooting clouds in the sky you want to frame your scene in a way that incorporates most of the sky in order to feature the clouds in context. Also choose a day where the clouds look like cotton balls because they typically move the fastest in the sky and are the easiest subject to make a time-lapse with.
Once you’ve done the preceding steps you need to set up your intervalometer. Depending on that camera you are using it can either be built into the cameras software, a firmware add-on, a phone app you need to download, or a separate remote that you need to connect to your camera. After you’ve done your research on how to shoot time lapses on your camera you need to then set the interval to take a photograph every 2 seconds for 240 photos over a period of 8 minutes. Once you’ve set those parameters you can activate the intervalometer to start your time-lapse. Make sure you stay close to the camera during the entire event to make sure it is not bumped into or knocked over.
After you’ve captured all of your images it is time to bring them into post production. Most editing programs such as Final Cut Pro, Premiere Pro, and Davinci Resolve will allow you to construct a time-lapse using the images you’ve captured. In this article I will cover how to do post production in Premiere Pro and DaVinci Resolve. The following are not endorsements but examples of the post workflows you might encounter.
In Premiere Pro you start by opening up the program and creating a new sequence.
You then set the frame rate to a preset of either 23.976 fps or 24 fps. (23.976) allows for easy conversions to other common frame rates without technical issues or a change in run time.). Also name your sequence.
File>import>find photos and click the first image in the series>check image sequence then import.
Premiere Pro defaults image sequences to 29.97 so you have to change the frame rate to 23.976.
Right click over the frame rate and select modify> timecode.
Click on the interpret footage tab and check “assume this frame rate…”. Type 23.976 then ok.
Render your sequence and then export to the location you want to save it.
In DaVinci Resolve you start your project by clicking File> Project Settings.
Set your frame rate to 24 FPS.
Select all of your images and then drag them into the media pool.
Double click the thumbnail and then drag the footage from the preview window to the timeline.
Go over to the deliver tab at the bottom of the screen, hit browse to choose your file location, and click ok.
Click start render.
Once it is complete check where you saved the file on your computer to make sure it plays smoothly.