A time lapse calculator resolves the four numbers that govern any interval sequence: how long you shoot, how often you fire, how long the finished clip runs, and how many frames that costs. Fix any three and the fourth is determined. Get them wrong on location and you discover the problem hours later, when four hours of shooting has produced a nine second clip or filled the card at the sixty per cent mark.
Arb Digital publishes this in its free tools library beside the image file size calculator, which sizes individual stills, and the video file size calculator, which sizes the rendered output rather than the frames that went into it. This page plans the capture. It does not process footage, and it does not convert between frame counts and running timecode — the timecode calculator handles that.
What This Time Lapse Calculator Does
It takes your shooting window, interval and playback frame rate and returns the clip length, the frame count and the speed-up factor. It then solves the problem backwards: given a clip length you want, it reports the interval that would deliver it from the same shooting window. Finally it applies your file size to give total card space, and compares that against a card capacity so you know before you start whether the sequence fits.
Both directions matter because time lapse planning genuinely runs both ways. Sometimes the shooting window is fixed — a sunset lasts as long as it lasts — and you need to know what interval produces a usable clip. Sometimes the clip length is fixed by an edit and you need to work out how long to stand there. Calculators that only solve one direction force you to guess and iterate.
The card capacity comparison uses decimal gigabytes, where one gigabyte is 1,000 megabytes, because that is how memory card capacities are marketed. Operating systems frequently report the same card in binary gibibytes, which is why a card sold as 128 GB shows as roughly 119 in a file manager. Neither figure is wrong; they count differently, and the difference is about seven per cent.
How to Use It
- Enter the real shooting window, not the ideal one. Battery life, light and access usually cut it short. Planning for four hours and getting two and a half halves your clip.
- Set the interval to something your camera can actually sustain. The interval is measured shutter to shutter and must be longer than the exposure plus the write time. A thirty second exposure cannot be repeated at a twenty second interval.
- Pick the playback rate the edit will use. Twenty-four is the cinema convention, twenty-five and fifty are the historic PAL rates, and 29.97 and 59.94 are the NTSC rates that carry all the drop-frame timecode complications with them.
- Use the target clip length to work backwards. If the edit needs a ten second shot, read the interval that produces it rather than shooting at a habitual five seconds and discarding most of the frames.
- Check the card figure before you leave. Raw files at twenty-five megabytes each add up faster than intuition suggests, and swapping a card mid-sequence produces a visible jump.
The Formula / How It's Calculated
All four relationships come from two divisions.
Frames = shooting time in seconds ÷ interval in seconds, and clip length in seconds = frames ÷ playback frame rate. Substituting one into the other gives clip length = shooting time ÷ (interval × frame rate), which means the denominator — interval multiplied by frame rate — is exactly the speed-up factor.
Reversing for a target clip length: required interval = shooting time ÷ (target clip length × frame rate). Storage is simply frames × file size per frame.
Worked example, matching the values the page loads with. Four hours is 14,400 seconds. At a five second interval that is 14,400 ÷ 5 = 2,880 frames. Played at 24 fps the clip runs 2,880 ÷ 24 = 120 seconds, or two minutes, and the speed-up factor is 5 × 24 = 120×. At 25 MB per raw file the sequence needs 2,880 × 25 = 72,000 MB = 72 GB, which is 56.3 per cent of a 128 GB card. To land a thirty second clip instead, the required interval is 14,400 ÷ (30 × 24) = 20 seconds, which would cut the frame count to 720 and the storage to 18 GB. The playback rates offered here trace back to the broadcast standards set out in ITU-R Recommendation BT.601, which fixed the studio encoding parameters that 25 and 29.97 fps still derive from.
Choosing an Interval by Subject, Not by Habit
The interval is the only genuinely creative number on this page, and picking it from habit is the most common reason a sequence fails. What matters is how far the subject moves between frames relative to the frame itself.
Fast-moving cloud and busy pedestrian traffic want something in the one to two second range. Anything longer and a cloud crosses a meaningful fraction of the frame between exposures, which reads as stuttering rather than motion. Ordinary drifting cloud, street traffic and shadows moving across a building sit comfortably between three and five seconds. Sunsets and sunrises want ten to fifteen, because the interesting change is the colour rather than the position of anything. Star trails and night sky work at twenty to thirty seconds, largely because the exposure itself is that long. Construction and plant growth run in minutes or hours.
The test to apply is subject displacement. If the thing you are watching moves more than roughly one to two per cent of the frame width between consecutive exposures, the result will strobe. That is why a long lens needs a shorter interval than a wide one on the identical subject: the same physical movement covers far more of a tight frame.
There is a related trick worth knowing. Shooting at a shorter interval than you need and discarding frames in post is always possible; shooting at too long an interval cannot be fixed at all. When you are unsure and the card allows it, err short. The camera field of view calculator gives the frame width in metres at your distance, which turns the one-to-two-per-cent guideline into an actual measurement.
Shutter Angle, Flicker and Why Time Lapse Looks Choppy
A time lapse can be perfectly calculated and still look wrong, and the usual cause is that each frame is too sharp.
Ordinary video shot at 24 fps with a 180 degree shutter uses an exposure of 1/48 second, so each frame contains a small amount of motion blur and consecutive frames flow into each other. A time lapse frame shot at 1/500 second freezes everything, and when those frozen frames are played back the eye sees a sequence of separate stills rather than continuous movement. This is why professional sequences often use neutral density filters to force a longer exposure — not for brightness but for blur. Aiming for an exposure of roughly a third to a half of the interval reintroduces enough blur to smooth the motion. The exposure value calculator gives the corrected shutter time for any filter strength, and Stanford's CS178 notes on the variables that affect exposure cover how shutter duration and motion blur relate.
Flicker is the second classic problem, and it comes from the aperture. Electronically controlled diaphragms do not stop down to precisely the same position on every actuation, and a variation of a few per cent between frames produces a visible pulsing across hundreds of frames. Shooting in full manual with a fully manual lens removes the cause. The common workaround with autofocus lenses is to stop down, press the depth of field preview, and detach the lens slightly so the aperture stays mechanically fixed — effective, and hard on the mount.
Holy grail sequences, which run from daylight into darkness, add a third difficulty. The light changes by ten or more stops during the shoot, so exposure has to ramp, and doing that in discrete steps produces steps in the finished clip. Deflicker processing in post is generally required no matter how carefully the ramp is executed.
The Practical Limits: Battery, Buffer and Shutter Life
The arithmetic will happily tell you that a twelve hour shoot at a one second interval produces 43,200 frames. Several physical realities will not cooperate.
Mechanical shutter life is the one people forget. A consumer camera is typically rated somewhere between 100,000 and 200,000 actuations, and a professional body around 400,000. At 2,880 frames per sequence, fifty time lapses consume a meaningful slice of that. Cameras with a genuine electronic shutter avoid the wear entirely, which is one of the strongest practical arguments for using one here.
Battery life falls faster than the frame count suggests, because the camera is awake between frames as well as during them. Cold makes it far worse — sub-zero conditions can halve usable capacity — which is why long sequences generally run from a mains adapter or a dummy battery fed by a power bank.
Write speed sets a hard floor under the interval. A camera writing 25 MB raw files to a card sustaining 40 MB per second needs well over half a second per frame before it can even think about the next exposure, and intervals under about one and a half seconds start to depend on buffer depth. Shooting compressed raw or JPEG relaxes this considerably at some cost in grading latitude.
Finally, plan the render. A 2,880 frame sequence at full resolution is a substantial amount of data to process, and the finished clip is a fraction of that size. Size the delivered file with the video file size calculator and check the delivery bitrate with the streaming bitrate calculator before committing to a resolution.
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See Web Design Services Talk to Arb DigitalCommon Mistakes to Avoid
- Setting an interval shorter than the exposure plus write time — the camera silently skips frames, and the sequence ends up with irregular gaps that read as jumps.
- Confusing the shooting frame rate with the playback frame rate — the interval governs capture, and only the playback rate determines how long the finished clip runs.
- Freezing every frame with a fast shutter — with no motion blur the clip stutters, which is why long sequences often use neutral density filters to lengthen the exposure deliberately.
- Shooting an aperture-controlled lens in a mode that re-stops each frame — small variations between actuations produce visible flicker across hundreds of frames.
- Sizing the card in binary gigabytes against a decimal capacity — a card sold as 128 GB reports as about 119 in most operating systems, and assuming the larger figure fills it early.
Related Free Tools From Arb Digital
Size individual files with the image file size calculator and the finished clip with the video file size calculator, then check delivery with the streaming bitrate calculator. Convert frames to running time with the timecode calculator, plan exposure and filters with the exposure value calculator, set focus with the hyperfocal distance calculator, and check framing with the camera field of view calculator. Everything else is in the free online tools hub.
Frequently Asked Questions
It depends on how fast the subject crosses the frame. Fast cloud and pedestrian traffic want one to two seconds, ordinary cloud and street traffic three to five, sunsets ten to fifteen, and night sky twenty to thirty because the exposure itself is that long. The test is whether the subject moves more than about one to two per cent of the frame width between frames.
At a five second interval and 24 fps playback, four hours produces 2,880 frames and a clip of exactly two minutes. Change either the interval or the playback rate and the length changes in direct proportion, since clip length equals shooting time divided by interval times frame rate.
It is the interval multiplied by the playback frame rate, and it tells you how much faster than real time the clip runs. Below about thirty times the result reads as sped-up video rather than a time lapse, and above a few thousand the movement blurs into something illegible.
Almost always because each frame is too sharp. A fast shutter freezes everything, so consecutive frames have nothing to flow between them. Aiming for an exposure of roughly a third to a half of the interval, usually by adding a neutral density filter, reintroduces the motion blur that makes movement read as continuous.
Usually the aperture. Electronically controlled diaphragms do not close to precisely the same position on every shot, and a few per cent of variation pulses visibly across hundreds of frames. Fully manual lenses avoid the cause entirely, and deflicker processing handles what remains.
Because capacities are marketed in decimal gigabytes of 1,000 megabytes while most operating systems report binary gibibytes of 1,024. A card sold as 128 GB shows as roughly 119, a difference of about seven per cent, and formatting overhead takes a little more.
Mechanical shutters are rated for a finite number of actuations, commonly 100,000 to 200,000 on consumer bodies and around 400,000 on professional ones. A single 2,880 frame sequence is a small fraction of that, but the habit adds up quickly. A true electronic shutter removes the wear altogether.
No, and it does not need to. Clip length here is a plain division of frames by frame rate. Converting a frame count into the running timecode a broadcast edit expects, including drop-frame counting at 29.97 and 59.94, is a separate calculation handled by a timecode tool.
