β³ Long Exposure Timer
Bulb-mode timer with progress bar and audio alert. Pairs with our ND filter calculator.
Ready. Set a duration and press Start.
Tip: test the beep with the 10-second warning on a short trial run. Keep your screen awake during the exposure.
How to Use This Timer
Long exposures live or die by timing: a 4-minute exposure that runs 4:20 is a third of a stop overexposed, enough to blow out highlights you cannot recover. This timer replaces mental counting and glancing at your watch. Set the target duration, choose count-down for planned shots or count-up for open-ended ones like light painting, and press Start when you open the shutter. A progress bar fills as time passes, a warning sounds ten seconds before the end, and a clear triple beep marks the target.
Enter your planned exposure in hours, minutes, and seconds. If you used an ND filter calculator, type in the adjusted shutter time it gave you.
Pick the mode. Count down to target stops the display at zero with a triple beep. Count up beeps at the target and keeps running so you can extend light painting or firework bursts by feel.
Set the camera to Bulb, lock the remote release open, and press Start at the same instant. Keep the phone screen awake and the volume up.
When you hear the 10-second warning, get your hand on the release. At the final beep, close the shutter. Press Reset to clear the timer for the next frame.
Why Timing Matters More Than You Think
Exposure errors scale with the length of the shot. Being 20 seconds late on a 4-minute exposure is only a tenth of a stop, harmless. But being 20 seconds late on a 30-second exposure is two thirds of a stop, very visible. The real danger zone is the 1 to 3 minute range, where people estimate "about two minutes" from a wristwatch and routinely miss by 15 to 30 seconds. A dedicated timer removes that guesswork entirely.
There is a second reason precision matters: repeatability. When you bracket long exposures, or shoot a series for stacking to reduce noise, every frame needs the same duration so the frames blend cleanly. Counting in your head while standing in the cold produces 3:47, 4:12, and 3:58. The timer produces 4:00 three times in a row, and your stacked result is cleaner for it.
Worked Example
You are shooting a waterfall at dusk. Your metered exposure without a filter is 1/4 second, and you mount a 10-stop ND filter. Each stop doubles the time, so 10 stops multiplies 0.25 seconds by 2^10 = 1024, giving 256 seconds, or 4 minutes 16 seconds. Enter 0 hours, 4 minutes, 16 seconds, choose count down, and start the timer as you lock the shutter open.
At 4:06 elapsed the 10-second warning beeps and you move to the tripod. At 4:16 the triple beep sounds and you release the shutter. The frame is exposed exactly as calculated, and the histogram confirms it. For the next composition you press Reset, enter the new duration, and repeat: no mental math, no watch checking in the dark.
Practical Tips
Cover the viewfinder during exposures longer than 30 seconds; light leaking in through the eyepiece can fog the frame, and most cameras ship with a little eyepiece cover for exactly this reason. Turn off long-exposure noise reduction only if you understand the trade: it doubles the time per shot (a 4-minute exposure becomes 8 minutes with the dark frame), but it removes hot pixels and amp glow that stacking cannot always fix.
For exposures past 5 minutes, watch for reciprocity failure with film, and with digital watch the battery: bulb mode with the sensor energized drains power fast, so start with a full battery and carry a spare in cold weather. If you shoot seascapes, time your exposure to cover complete wave cycles, typically 2 to 4 minutes, so the water renders as smooth glass instead of half-frozen chop.
Frequently Asked Questions
How do I use bulb mode with this timer?
Set your camera to Bulb (B) mode, frame and focus the shot, then press the shutter with a remote release that locks open. Start this timer at the same moment. When the timer beeps and the progress bar fills, release the shutter lock. The timer and a locking remote together replace an expensive intervalometer for single long exposures.
Should I use count-up or count-down mode?
Count-down is best when you have a planned exposure, for example a 4-minute shot calculated with an ND filter. Count-up is better for open-ended exposures like light painting or fireworks, where you watch the scene and stop when it looks right. In count-up mode the timer still beeps at your target duration as a reference point, then keeps counting.
Will the timer keep running if my phone screen locks?
Most mobile browsers pause or throttle JavaScript timers when the screen locks or the tab goes to the background, so keep the screen on during the exposure. Plug the phone in for very long exposures, disable auto-lock temporarily, and treat the timer as your primary timekeeper with your watch as backup on critical shots.
Does the beep work without internet?
Yes. The alert is generated with the Web Audio API, which synthesizes the tone directly in your browser with no audio files and no network requests. It works fully offline as long as the page itself has loaded. Make sure your device volume is up and silent mode is off, since mobile silent switches mute web audio.
How accurate is a browser-based timer?
Within a fraction of a second for exposures under about 30 minutes, which is far more precise than counting in your head and easily good enough for photography. The display updates several times per second using the system clock, so brief background hiccups correct themselves instead of accumulating drift. For exposures longer than an hour, use a dedicated intervalometer.
What is the 10-second warning for?
Long exposures end abruptly, and fumbling for the shutter release in the dark can shake the camera. The warning beeps ten seconds before the target give you time to get your hand on the release, steady the tripod, and close the shutter exactly on time instead of reacting late to the final beep.