How to Shoot a Timelapse: From Interval Maths to Flicker

You’ve seen the videos: clouds pouring over a mountain ridge, a city’s lights switching on in seconds, stars sweeping an arc across the sky. None of them needed a special camera. They all come from the same simple idea: lock the camera down, shoot hundreds of photos at a fixed interval, then play those photos back as video frames. Time compresses.

Let’s clear up a confusion first, because these two get mixed up constantly:

• A long exposure is one frame. The shutter stays open for 30 seconds and everything that moves leaves a trail in that single frame. The result is a photograph.
• A timelapse is hundreds of frames. Each frame is an ordinary photo on its own; what gets compressed is the gap between frames. The result is a video.

If it’s motion trailing within a single frame you’re after, the long exposure guide covers that. This article is about the art of setting a camera up and walking away.

One formula: how many frames, how much video?

All of timelapse is the relationship between three numbers: the interval (time between frames), the frame count, and the fps of your video (usually 25 or 30).

The only equation you need is this:

Flipping it around is more useful for planning:

• Frame count = target clip length × fps. A 10-second clip at 25 fps needs 250 frames.
• Shooting time = frame count × interval. Those 250 frames at a 3-second interval mean 750 seconds — 12.5 minutes standing in the field.

A few concrete examples, for working it out in your head on location:

Subject	Interval	Frames	Shooting time	Clip (25 fps)
Moving clouds	3 s	300	15 min	12 s
Sunset	4 s	450	30 min	18 s
City sliding into blue hour	5 s	600	50 min	24 s
Star movement	25 s	400	2 h 47 min	16 s

How do you choose the interval?

The right interval is the longest value at which the fastest motion in your scene still flows without stepping. Too short and you get thousands of pointless frames and a video that looks sluggish; too long and the motion stutters.

Subject	Interval
Crowds, traffic, fast-moving cloud	1-2 s
Sunset, medium cloud, sea	2-5 s
Shadows rotating, harbours, distant ships	5-15 s
Stars, Milky Way	20-35 s (20-30 s exposure + short gap)
Plant growth, construction, a flower opening	5 min - 1 hour

The night-sky row is so different for a simple reason: there, the interval isn’t your choice, the exposure sets it. You’re already giving stars 20-30 seconds, so the interval has to sit just above that. The reasoning behind those settings is in Milky Way settings.

Making motion flow: why a short exposure hurts

First timelapses usually have an odd stop-motion feel — motion stutters instead of flowing. The cause is almost always an exposure that’s too short.

Video has an equivalent idea: the 180° rule says to keep your shutter speed near 1/(2 × fps), because a certain amount of motion blur in each frame is what lets the eye read motion as smooth. The same logic applies to timelapse, just at a different scale: the closer your exposure gets to half the interval, the smoother the motion.

So on a 2-second interval you don’t want 1/500 s — you want something around 1 second. Clouds pour, water turns to silk, crowds drift through like ghosts.

The only obstacle is light: in daylight, even at ISO 100 and f/11, your shutter speed sits around 1/250 s. Getting to 1 second needs 6 to 10 stops of ND. How to work out the density you need is in the ND and polarizing filter guide, and for estimating daylight in your head the Sunny 16 rule does the job.

Flicker: the number one killer of timelapses

Each frame looks perfect on its own, but play the video back and the image pulses brighter and darker throughout. This is flicker, and it’s far harder to fix than to prevent. The causes, in order:

1. Auto exposure. The camera re-meters every frame and hands you tiny differences. Across 300 frames that becomes visible pulsing. Fix: manual mode, fixed aperture, fixed shutter, fixed ISO.

2. Auto white balance. Colour jumps from frame to frame. Fix: lock WB in Kelvin — the white balance guide covers which value suits which light.

3. Aperture blade flicker. This is the sneaky one. Lenses with electronic apertures re-close the diaphragm for every frame, and the blades don’t land in precisely the same place each time. The result is small, irregular brightness variation. Three ways out:

• Shoot wide open. The diaphragm never closes, so the blades never come into play and there’s nothing to vary.
• Use a lens with a manual aperture ring. The ring stays put mechanically.
• The “lens twist” trick: set the aperture you want, then loosen the lens on the mount by a notch to break the electronic contact. The aperture freezes at that value. It carries a dust risk and behaves differently across systems, but it’s widely used.

4. Autofocus. AF re-focuses every frame and introduces micro-shifts. Lock focus and switch to manual; for finding correct focus in the dark, see focusing at night.

5. Image stabilisation. Left on while tripod-mounted, stabilisation nudges the image by microns between frames. Turn it off the moment you’re on a tripod — the reasons are in what is image stabilisation.

6. Artificial light. LED and fluorescent fixtures pulse at the mains frequency (50 Hz across most of the world, 60 Hz in North America). For interiors or street-lit scenes, keep your shutter speed at multiples of 1/50 s (or 1/60 s), or go past one second — a long exposure averages the pulsing out by itself.

Day to night: the “holy grail”

A timelapse that runs unbroken from sunset into a starry sky is the hardest test in this discipline, and it has a name in the literature: the holy grail. The reason: light changes by more than 10 stops between those two points. Start with fixed settings and either the daylight half blows out white or the night half stays black.

Three approaches:

• Manual bumping: while the sequence runs, you add a third of a stop of ISO or shutter every 30-60 seconds to follow the light. Each intervention leaves a small step in the video, which you smooth out later with deflickering.
• Semi-automatic: aperture priority plus auto ISO. The camera tracks the light but flicker rises sharply, so deflickering becomes mandatory.
• Dedicated software: tools like LRTimelapse manage the transition deliberately. Serious work goes this route.

Cards, batteries and file maths

Hundreds of frames means a completely different resource load from ordinary shooting:

• File size: on a 24 MP body a RAW frame runs about 25 MB. 500 frames = 12.5 GB. Shoot three clips in an evening and you’re past 40 GB. The memory card guide helps with capacity and speed choices.
• Card speed: at a 2-second interval you’re writing roughly 12 MB/s continuously — any decent card handles it. But at a 1-second interval on a 45 MP body that becomes 45 MB/s, and a slow card will cost you frames.
• Battery: with live view and the screen off, a modern body can manage 800-1000 frames. In the cold, halve that. For long sequences, USB-C power delivery or a dummy battery plus power bank is close to essential.
• RAW or JPEG: in changing light — sunset, blue hour — RAW is non-negotiable, because you apply white balance and exposure to the whole sequence afterwards. For very long projects in steady light, JPEG is defensible; it cuts storage and processing load substantially. We weighed the trade-off in RAW vs JPEG.

Two modes in the camera menu: which one?

Most bodies offer two separate menu items with confusingly similar names:

• Interval shooting / Interval Timer: saves each frame as a separate photo. You can shoot RAW, deflicker afterwards, keep your crop headroom, and build the video at whatever fps you like.
• Time-lapse Movie: the camera assembles the frames internally and hands you a finished video file. It’s easy, but it’s JPEG-based: no RAW, no deflickering, no crop headroom, no going back.

The recommendation is clear: use interval shooting. The price of convenience can be a whole night’s work becoming unsalvageable.

If your body has no interval timer, a cheap external cable timer (an intervalometer) solves it, and many manufacturers’ phone apps will do the job too.

Setup order in the field

Step nine isn’t a joke. Half of timelapse is patience; the moment you touch the camera to “just fix the framing”, that clip is over.

Turning frames into video

Once the frames are shot, the work moves to the desk:

1. Open the RAWs, develop one frame and apply those settings to the whole sequence. Editing frame by frame is an invitation to flicker. The batch workflow is in RAW editing workflow.
2. If flicker remains, run a deflicker pass (LRTimelapse, or your editor’s deflicker plugin).
3. Import the frames as an image sequence and set 25 or 30 fps.
4. Optionally use your crop headroom to add a slow pan.
5. Soften the head and tail of the clip with a short transition.

Close relatives of the timelapse

Frames gathered with the same interval shooting produce completely different results depending on how you process them — so one night’s shoot can yield two finished pieces:

• Stack the frames and the stars’ movement merges into a single frame; the technique is in star trail photography.
• Scan the frames and pick the ones with meteors and you have a meteor shower photograph. The full setup for the Perseid peak on 12-13 August is in the Perseid meteor shower guide.

So if you shot 400 frames for the Perseids one night, you also have a 16-second sky timelapse and a star trail frame. Same effort, three outputs.

Common mistakes

• Leaving auto exposure or auto WB on: the two most common causes of flicker. Manual mode and manual Kelvin aren’t up for debate.
• Setting the interval too close to the exposure: the camera silently drops frames and the clip’s rhythm breaks. Stick to exposure + 2 seconds.
• Shooting too few frames: 100 frames is 4 seconds of video. Shoot at least 125, ideally 250+.
• Shooting stopped down on an electronic aperture: blade flicker is then unavoidable. Shoot wide open or fix the aperture mechanically.
• Leaving stabilisation on while on a tripod: invisible in stills, but it treats frame-to-frame drift as something to correct.
• Not doing the battery and card maths: a battery that dies in minute 40 of a 45-minute sequence throws the whole clip away.
• Fixing the framing mid-sequence: the clip splits in two right there. Get it right at the start, then leave it alone.
• Ignoring which way the clouds are going: if clouds aren’t entering and leaving the frame, there’s no motion in the video. Frame toward where the motion is coming from.