Long exposure photography turns moving water into silk, transforms busy streets into ghostly trails of light, and renders moving clouds as painterly streaks across a still sky. The technique is straightforward once you understand the tools: a solid tripod, the right ND filters, and an accurate exposure calculation method. Here is the complete workflow.
What is Long Exposure Photography?
Long exposure is any exposure lasting longer than about 1/30 second where subject movement becomes a creative element. The most common long exposure effects:
- Silky water: Waterfalls, rivers, and waves rendered as smooth, flowing silk. Typically requires 1/4 second to 4 seconds depending on water speed. Faster-moving water silks at shorter exposures; slow-moving water needs 2–8 seconds.
- Cloud streaks: Cumulus clouds rendered as horizontal streaks across the frame. Requires 30 seconds to several minutes depending on cloud speed and direction. Best during weather transitions when clouds move quickly.
- Light trails: Car headlights and taillights rendered as continuous orange and red trails. Best during blue hour. 10–30 second exposures on a moderately busy road.
- Star trails: Earth’s rotation recorded as concentric arcs of stars around the celestial pole. Requires 15 minutes to several hours of continuous exposure or stacked frames.
The ND Filter: Your Primary Tool
A neutral density (ND) filter is a darkened glass element that reduces the amount of light entering the lens without affecting color. It extends your required exposure time by a predictable amount. ND filters are rated in stops of light reduction:
| ND Rating | Stops Reduced | Light Reduction | Use Case |
|---|---|---|---|
| ND4 | 2 stops | 75% | Very subtle; mostly for bright portraits |
| ND8 | 3 stops | 87.5% | Waterfall silking in shade; some video |
| ND64 | 6 stops | 98.4% | Most versatile for landscape long exposure |
| ND400 | 8–9 stops | 99.8% | Extended waterfall and water movement |
| ND1000 | 10 stops | 99.9% | Dramatic cloud and water; daylight 2–30 min |
| ND100000 | 16+ stops | 99.999% | Solar imaging (requires solar-specific filter) |
The 6-Stop ND (ND64): Most Versatile for Landscape
The 6-stop ND is the most versatile single long-exposure filter for landscape photography. At typical daylight exposures (1/250s base), a 6-stop ND extends your time to 1/4 second — enough for water silking. At golden hour (1/30s base), it extends to 2 seconds — enough for significant cloud movement and silky water. It is neutral enough to use without an app-based calculation (you can calculate the extended time by doubling six times: 1/250 → 1/125 → 1/60 → 1/30 → 1/15 → 1/8 → 1/4).
Recommended 6-stop ND filters by quality tier:
- Professional: Kase Wolverine 6-stop ND (~$140–$180), NiSi 6-stop ND Pro Nano (~$120–$160)
- Mid-range: Hoya ProND 64 (~$80–$100), Breakthrough Photography X4 6-stop (~$90)
- Budget: K&F Concept 6-stop ND (~$30–$50) — acceptable color neutrality; may have slight warming cast that is correctable in post
The 10-Stop ND (ND1000): Dramatic Long Exposures
The 10-stop ND is the signature tool for dramatic minimalist long exposure photography — the images of impossibly smooth water under a bright sky, or cloud streaks that transform a mundane building into an ethereal composition. At a base exposure of 1/250s in full sun, a 10-stop ND requires a 4-second exposure. At 1/30s (golden hour), it requires 30 seconds. At ISO 100 in midday sun at f/11, it may require several minutes — use a dedicated app to calculate accurately.
Calculating Extended Exposure Time
The Manual Calculation
For 6-stop filters, manual calculation is fast: take your base exposure time and double it six times. 1/250s → 1/4s. 1/60s → 1s. For 10-stop filters, double ten times — the math becomes unwieldy, which is why apps exist.
App-Based Calculation
- Long Exposure Calculator: Free iOS/Android. Input your base exposure (without ND) and your filter strength (stops). The app calculates the required extended exposure. Also handles multiple filters stacked together.
- ND Calculator: Similar functionality, also handles fractional stop filters.
- PhotoPills: Comprehensive photo planning app (paid, ~$10) that includes ND filter calculation alongside sun/moon positioning, depth of field, and star trail calculators. The most complete planning tool for landscape and long exposure photographers.
- Lumu Power: A physical light meter attachment for smartphones that gives precise incident light readings for accurate base exposure before applying the ND filter calculation.
Complete Long Exposure Workflow
- Set up composition on tripod. Confirm camera is level. Enable the grid display.
- Compose and focus WITHOUT the ND filter. ND filters, especially 10-stop, make Live View too dark to focus through. Focus manually or with autofocus, then switch to manual focus and tape the focus ring.
- Set exposure WITHOUT ND filter. In Manual mode: set f/8, ISO 100, and adjust shutter speed until the histogram looks correct (slightly right of center without blowing highlights). Note this exposure — this is your base.
- Calculate extended exposure. Use app or mental calculation. Add 6 stops to the base for a 6-stop ND, 10 stops for a 10-stop ND.
- Attach the ND filter. Do not touch focus or aperture.
- Set extended shutter speed. If your calculated time is 30 seconds or less, set it on the camera. If longer, use Bulb mode (see below).
- Fire with cable release or 2-second timer. Never touch the camera during the exposure.
- Review on LCD. Check exposure with the histogram — the histogram after ND filtering should look the same as your base exposure without the filter. If it is left-heavy (underexposed), recalculate — your ND filter may not be precisely the stated stop value.
Bulb Mode for Exposures Over 30 Seconds
Standard shutter speeds on most cameras max at 30 seconds. For exposures longer than 30 seconds (cloud streaks, star trails, ultra-smooth water), use Bulb mode (BULB on the mode dial or by scrolling past 30″ in Manual mode).
In Bulb mode, the shutter stays open as long as you hold the shutter button pressed (or as long as a cable release holds it open). A locking cable release — one that can be locked in the down position — is essential for exposures over 30 seconds. Without a cable release, you must hold the shutter button, introducing camera shake.
Set the release: press and lock, start a timer on your phone or use the camera’s interval timer to count down the calculated exposure, then release when the time is up.
Graduated ND Filters for Sky-Ground Balance
A graduated ND filter (GND) darkens only part of the frame — typically the sky — leaving the foreground at normal exposure. This addresses the dynamic range problem in landscape photography where the bright sky and darker ground cannot both be exposed correctly in one frame without digital manipulation.
Hard GND vs Soft GND: Hard-edged GNDs have an abrupt transition — useful for scenes with a distinct horizon line (ocean, flat landscape). Soft-edged GNDs have a gradual transition — better for scenes with irregular foreground elements (mountains, trees) that extend above the horizon. The Kase Armour and NiSi soft-edge GND filters are the most widely recommended in the landscape photography community.
For the camera settings and additional techniques for night and long exposure photography, see our night photography settings guide. For landscape photography workflow including focus stacking, see our Sony A7 IV landscape settings guide.
Frequently Asked Questions
What ND filter do I need for waterfall photography?
A 6-stop ND (ND64) is the most versatile — it extends typical daylight exposures (1/250s) to 1/4 second, enough for water silking in most conditions. The 10-stop ND creates longer exposures that completely smooth water but may lose all texture and movement detail.
How do I calculate long exposure time with an ND filter?
Find your base exposure without the ND filter. Then double the exposure time once per stop of ND. For 6 stops: double six times. For 10 stops: double ten times. Use a Long Exposure Calculator app for accuracy with 10-stop or stacked filters.
Can I use more than one ND filter at the same time?
Yes — stacking adds the combined stops. A 6-stop + 3-stop = 9 stops total. Tradeoffs: potential light leaks and vignetting with multiple filters. A single 10-stop filter is generally preferable to stacking.
Why are my long exposure photos blurry?
Camera movement during exposure (use a cable release), focus set incorrectly before attaching ND (always focus without ND), IBIS not turned off on tripod, or wind vibration on a light tripod. Add weight to the tripod center hook; lower the tripod height to reduce vibration leverage.
How long of an exposure do I need for silky waterfall photography?
1/4 second to 4 seconds for most waterfalls. Fast waterfalls silk at 1/4–1/2 second. Moderate falls need 1–2 seconds. Very slow-moving water needs 4–8 seconds for full silking. Each waterfall is different — experiment.
