Long Exposure Calculator

Neutral density (ND) filters block light so a shutter can stay open far longer than an unfiltered meter reading allows, and this calculator converts a metered base exposure time and an ND filter strength into the new shutter speed needed for correct exposure with the filter attached. Whether the goal is smoothing water, streaking clouds, or eliminating moving people from a scene, knowing the precise exposure time in advance prevents wasted shots and bracketing guesswork.

• A base shutter speed can come from a standard list or a custom value, accepting fractions like 1/125, decimals like 0.008, or whole numbers like 2.
• ND filters come from a preset list, a custom stop count, or a stack of several filters combined, with the stops of each stacked filter added together automatically.
• Results display the new exposure time in both exact seconds and a human-readable hours, minutes, and seconds format.
• An ND filter reference table lists the adjusted exposure across every common ND filter strength for the current base shutter speed, making it easy to compare filters at a glance.
• The core formula: New Exposure equals Base Exposure multiplied by 2 raised to the power of ND stops. For example, a 1/8 second base exposure with a 6-stop ND64 filter gives 1/8 multiplied by 64, which equals 8 seconds.

Plan exposure in advance to save time in the field and reduce trial-and-error shooting. Long exposure photography opens creative possibilities that are impossible to achieve with normal shutter speeds, and accurate ND filter compensation is essential whenever ambient light, motion, or filter stacking pushes shutter speeds past what a camera meter can read directly.

• Landscape Photography: Calculate multi-second exposures to smooth ocean waves, rivers, and waterfalls into silky textures. A 10-stop ND1000 filter transforms a 1/125 second reading into an 8 second exposure for dramatic water effects.
• Cityscape and Architecture: Determine exposure times of 30 seconds or longer to remove pedestrians and vehicles from busy urban scenes. Stacking a 6-stop and a 10-stop filter for 16 stops total achieves several-minute exposures during daylight.
• Cloud Streaking: Plan 2 to 5 minute exposures that transform static clouds into dynamic streaks across the sky, adding motion and drama to otherwise still compositions.
• Fine Art Photography: Explore extreme long exposures of 10 minutes or more using 15 or 20 stop filters to create ethereal, minimalist images where all motion dissolves into soft gradients.
• Astrophotography Transitions: Compute twilight long exposures during blue hour by combining ND filters with longer base exposures to balance ambient and artificial light.
• Education and Learning: The step-by-step derivation shows the mathematical relationship between stops, filter factors, and exposure times; the reference table gives a complete overview when comparing filter strengths.
• Filter Purchase Planning: Compare values in the reference table to decide which ND filter strengths suit typical shooting conditions and desired exposure ranges.