Question 1

How does the ND filter exposure calculation work?

Accepted Answer

Every stop of ND filtration halves the light reaching the sensor, so the shutter speed must double to compensate. The formula is: new shutter speed = base shutter speed × 2^stops. For example, a 6-stop ND filter on a 1/60s base exposure gives 1/60 × 2^6 = 1/60 × 64 ≈ 1.07s.

Question 2

How do I find my base shutter speed?

Accepted Answer

Meter your shot normally, without the ND filter mounted, using your camera's regular metering (aperture priority or manual with a light meter reading). Enter that value here as either a fraction (e.g. "1/125") or decimal seconds (e.g. "2.5"), then select your filter strength to get the new exposure time.

Question 3

What is the difference between ND2, ND1000, and "6-stop" or "10-stop" naming?

Accepted Answer

Manufacturers label filters two ways: by filter factor (ND2, ND4, ND8... where the number is how many times dimmer the filter makes the scene) or by stops (each stop is a doubling, so filter factor = 2^stops). A "10-stop" filter is conventionally sold as ND1000, even though 2^10 is technically 1024 — the ND number is a rounded marketing label. This calculator uses stops as the source of truth so results are always exact.

Question 4

When do I need Bulb mode?

Accepted Answer

Most cameras only offer shutter speeds up to 30 seconds natively. Any calculated exposure longer than 30 seconds requires switching to Bulb mode with a remote shutter release or intervalometer to hold the shutter open manually for the calculated time. This calculator flags that automatically.

Question 5

Can I stack multiple ND filters?

Accepted Answer

Yes — stacked filters add in stops (not multiply in filter factor labels). For example, stacking a 6-stop and a 3-stop filter gives 9 stops total. Enter the combined stop value using "Custom (enter stops)" mode to calculate the resulting exposure time.

Question 6

Is my data sent anywhere?

Accepted Answer

No. All calculations run entirely in your browser as plain JavaScript — nothing you enter is ever uploaded or stored on a server.

Filter	Stops	Factor
ND2	1	2×
ND4	2	4×
ND8	3	8×
ND16	4	16×
ND32	5	32×
ND64	6	64×
ND128	7	128×
ND256	8	256×
ND512	9	512×
ND1000 (Big Stopper)	10	1024×
ND2000	11	2048×
ND4000	12	4096×
ND8000	13	8192×
ND32000	15	32768×
ND64000	16	65536×
ND100000 (Super Stopper)	16.5	92682×

ND Filter / Long Exposure Time Calculator

How to Use

ND Filter Reference Chart

Frequently Asked Questions

How does the ND filter exposure calculation work?

How do I find my base shutter speed?

What is the difference between ND2, ND1000, and "6-stop" or "10-stop" naming?

When do I need Bulb mode?

Can I stack multiple ND filters?

Is my data sent anywhere?

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