Quick Reference

Base	ND8 (3 stops)	ND64 (6 stops)	ND1024 (10 stops)
1/8000	1/1000	1/125	1/8
1/4000	1/500	1/63	1/4
1/2000	1/250	1/31	1/2
1/1000	1/125	1/16	1s
1/500	1/63	1/8	2s
1/250	1/31	1/4	4s
1/125	1/16	1/2	8s
1/60	1/8	1s	17s
1/30	1/4	2s	34s
1/15	1/2	4s	1m 8s
1/8	1s	8s	2m 8s
1/4	2s	16s	4m 16s
1/2	4s	32s	8m 32s
1s	8s	1m 4s	17m 4s
2s	16s	2m 8s	34m 8s
4s	32s	4m 16s	68m 16s

What is this?

An ND (neutral density) filter is like sunglasses for your camera lens. It reduces the amount of light entering the lens without changing the colors, allowing you to use slower shutter speeds or wider apertures in bright conditions. This is how photographers create silky waterfalls, smooth oceans, or blurred clouds during the day.

How it works

ND filters are rated by how many stops of light they block. An ND2 filter (1 stop) halves the light, an ND8 (3 stops) reduces it to 1/8th, and an ND1000 (10 stops) reduces light by a factor of 1024. The naming conventions can be confusing: "ND8" means the filter factor is 8 (3 stops), while "ND 0.9" uses optical density notation (each 0.3 = 1 stop, so 0.9 = 3 stops). The resulting shutter speed is simply the base speed multiplied by the filter factor. For example, if your unfiltered exposure is 1/125s and you add a 10-stop ND (ND1000), the new shutter speed is 1/125 x 1024 = approximately 8 seconds. Stacking multiple ND filters adds their stop values together but can introduce vignetting and color casts, especially with wide-angle lenses.

Key factors

Base Shutter Speed — The correct exposure time without any filter. Meter the scene first, then calculate the filtered exposure from this starting point.

Filter Strength — Measured in stops. Each stop doubles the exposure time. Common strengths: 3-stop (ND8), 6-stop (ND64), and 10-stop (ND1000).

Stacking Filters — You can combine filters by adding their stop values. A 3-stop + 6-stop stack gives 9 stops of reduction. Beware of vignetting on wide-angle lenses.

Pro Tip

Compose and focus before attaching a strong ND filter. With 10 stops of light reduction, your viewfinder and autofocus will struggle in the dark.

Pro Tip

For seascapes, 1-2 second exposures smooth small ripples into texture while retaining wave structure. Exposures of 30 seconds or more create completely flat, misty water.

Pro Tip

Cheap ND filters often add a color cast (usually magenta or brown). Invest in quality glass from reputable brands, or learn to correct the cast in post-processing using a gray card reference.

⚡Challengebeginner

You are at a waterfall and your camera meters a correct exposure at 1/125s without any filter. You attach a 3-stop ND filter (ND8). What is the new shutter speed?

Hint: Each stop doubles the exposure time. 3 stops means 2 x 2 x 2 = 8 times longer.

Base Shutter Speed

ND Filter

Resulting Shutter Speed1/16

Stops Added3

ND Filter Calculator

ND Filter Calculator

Quick Reference

ND Filter Calculator