ND Filter Exposure Calculator
Convert shutter speed after attaching ND filter and countdown long exposure timer
How to Use
- Input reference shutter speed (proper exposure without ND filter)
- Select the ND filter to attach by tapping (up to 3 filters can be stacked)
- Converted shutter speed, total stops, and factor are displayed instantly
- For exposures over 30 seconds, bulb exposure badge is shown and countdown timer can be started
- For goals like 'I want to shoot in 2 minutes', reverse calculation mode shows required stops and ND combination suggestions
Use Cases
- When wanting to instantly convert SS at long exposure sites where waterfalls, streams, ocean, and clouds are captured smoothly
- When wanting to know the total stops and exposure time of stacked ND filters
- When wanting to use a countdown timer instead of counting seconds for bulb exposure
- When wanting to reverse calculate required ND filter stops and combinations from target exposure time
Frequently Asked Questions
How many stops of reduction does ND1000 provide? ▼
ND1000 is conventionally treated as 10 stops (2^10 = 1024x). Although the rated number is 1000, the actual reduction is equivalent to 1024x, and this tool calculates it as 10 stops. For non-power-of-2 numbers like ND400 or ND500, calculation uses the actual factor (ND400 = 400x ≈ 8⅔ stops).
How is it calculated when stacking ND filters? ▼
Factors multiply and stops add. For example, stacking ND8 (3 stops) and ND64 (6 stops) results in 8×64 = 512x, or 3+6 = 9 stops of reduction. This tool supports up to 3 filters stacked.
How do you shoot exposures over 30 seconds? ▼
Most cameras have shutter speed settings up to 30 seconds, so anything longer must be managed manually using bulb (B) mode. This tool can start a countdown timer with one tap from the calculation result, and notifies you with a beep and vibration when complete. Wake Lock keeps the screen from turning off during measurement.
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