What is an ND (Neutral Density) filter?

A Neutral Density (ND) filter is a semi-transparent darkened glass placed in front of your camera lens. It uniformly reduces the amount of light entering the sensor without altering color balance, allowing photographers to use slow shutter speeds or wide apertures in bright sunlight.

How do you calculate exposure time with an ND filter?

Multiply your base (unfiltered) shutter speed by 2 raised to the power of the filter's stop rating: Adjusted Time = Base Speed × 2^stops. For example, 1/125s with a 10-stop filter equals (1/125) × 1024 ≈ 8.2 seconds.

What shutter speed makes waterfalls look silky smooth?

A shutter speed between 1/4 second and 2 seconds produces silky smooth, painterly waterfalls while retaining water texture. Shutter speeds longer than 5 seconds will render moving water as a misty, ethereal fog.

Can I stack multiple ND filters?

Yes! When stacking filters, simply add their stop ratings together. A 6-stop ND64 stacked with a 3-stop ND8 yields 9 total stops of light reduction.

ND Filter Calculator – Long Exposure Shutter Speed

Filter Parameters

Live Solver

Base Shutter Speed (No Filter) Metered Ambient

ND Filter Strength Optical Density

Custom Reduction (Stops)

Desired Target Shutter Speed Find Required ND

Adjusted Shutter Speed

8.2s

In-Camera Shutter

Total Light Reduction

10.0stops

Optical Power Factor

Filter Factor / Rating

ND1000

Density: 3.0 OD

Light Transmittance

0.098%

Reaches Sensor

Required Filter to Target

11.9stops

For selected target time

⏱️

00:08

Bulb Timer Ready

Water Blur Shutter Calculator & Motion Presets

1-Click Apply

🧊

Freeze Droplets & Splashes

1/1000s

Freezes crashing waves, ocean spray, and splashing streams in crisp crystal clarity.

🌊

Textured Water Motion

1/4s

Captures dynamic energy and white water trails without losing individual river contours.

💧

Silky Smooth Waterfall

2.0 seconds

The classic landscape favorite: velvety smooth cascades while keeping mossy rocks tack sharp.

🌫️

Misty Ocean Waves

10.0 seconds

Transforms ocean tide and coastline swells into a surreal, painterly fog around sea stacks.

🪞

Mirror Glass Lakes

30.0 seconds

Eliminates surface ripples and wind chop, producing reflections like polished glass.

☁️

Streaking Cloud Blur

2 minutes

Warps fast-moving sky clouds into dramatic, directional motion lines pointing toward the horizon.

ND Filter Strength Conversion Table

Universal Standard

Common Name	Stop Reduction	Filter Factor (ND)	Optical Density (OD)	Transmittance (%)	Base: 1/125s
1 Stop	1 Stop	ND2	0.3	50.0%	1/60s
2 Stops	2 Stops	ND4	0.6	25.0%	1/30s
3 Stops	3 Stops	ND8	0.9	12.5%	1/15s
4 Stops	4 Stops	ND16	1.2	6.25%	1/8s
5 Stops	5 Stops	ND32	1.5	3.13%	1/4s
Little Stopper	6 Stops	ND64	1.8	1.56%	0.5s
Big Stopper	10 Stops	ND1000	3.0	0.098%	8.2s
Super Stopper	15 Stops	ND32000	4.5	0.003%	4m 22s
Solar Filter	16.6 Stops	ND100000	5.0	0.001%	14m 38s

Complete Guide to ND Filters & Long Exposure Photography

A Neutral Density (ND) filter acts as sunglasses for your camera lens. By reducing the volume of light that hits the image sensor without tinting the color spectrum, ND filters give landscape, seascape, and architectural photographers full artistic control over shutter speed and aperture in broad daylight.

The ND Shutter Speed Formula

Adjusted Shutter Speed = Base Speed (No Filter) × 2^(Filter Stops)

For instance, if your meter reads 1/125s at f/8, adding a 10-stop ND filter multiplies the exposure duration by 2^10 = 1024:
(1 / 125) × 1024 = 8.19 seconds.

Understanding ND Naming Conventions

Different manufacturers label ND filters using three different rating systems:

Stops of Light: Commonly used by photographers (e.g. 3-stop, 6-stop, 10-stop). Each stop doubles exposure time.

Filter Factor (ND Number): Represents the light divisor. ND8 reduces light to 1/8th (3 stops, 2³ = 8); ND1000 reduces light to ~1/1000th (10 stops, 2¹⁰ = 1024).

Optical Density (OD): Scientific measurement where each 0.3 OD represents 1 stop (0.9 = 3 stops, 1.8 = 6 stops, 3.0 = 10 stops).

Tips for Sharp Long Exposures

Lock Down on a Sturdy Tripod: Any wind vibration during a 30-second exposure will blur your subject.

Cover the Viewfinder: On DSLR cameras, stray light entering through the optical viewfinder can leak onto the sensor, causing purple or magenta color banding.

Focus Before Attaching the Filter: A 10-stop filter is nearly black; autofocus systems will hunt and fail. Acquire focus in autofocus, switch your lens to manual focus (MF), and gently thread the filter onto your lens.

Frequently Asked Questions

A 6-stop filter (ND64) is ideal for golden hour, sunrise, sunset, or fast-flowing forest streams where you want 1/2s to 4s exposures. A 10-stop filter (ND1000) is meant for midday sun to achieve extreme exposures lasting 10 to 60+ seconds for mirror-like seascapes and ghosting moving people.

Most camera dials stop at 30 seconds. To expose longer, rotate your shutter wheel past 30s into Bulb (B) mode. In Bulb mode, the shutter stays open as long as the button is held down. Use a cable release or wireless remote shutter, and trigger the countdown timer on this page.

Stacking multiple glass filters adds extra reflective surfaces, which can introduce chromatic aberration, slight color casts, and corner vignetting on wide-angle lenses. High-quality multi-coated slim brass filters minimize these issues.