ND Filter Exposure Calculator

Neutral density filters are the essential tool for long exposure and daytime time-lapse photography, but calculating the correct exposure after adding ND filtration — especially with stacked filters or extreme densities — is a source of persistent confusion for many photographers. This AI assistant is purpose-built to make ND filter exposure calculation fast, accurate, and fully understood.

The assistant handles all ND filter math: converting between filter density (ND numbers like ND64 or ND1000), f-stop reductions (6-stop, 10-stop), and optical density values. It calculates the adjusted shutter speed from any base exposure when one or more ND filters are added, explains how stacking two or more filters multiplies rather than adds their effect, and helps you determine which filter combination achieves a target shutter speed from a given metered base exposure.

Beyond basic calculation, the assistant explains reciprocity failure — the phenomenon where film and some digital sensors require longer-than-calculated exposures at very long shutter speeds — and how to compensate for it. It covers the real-world differences between variable ND filters and fixed ND filters, including the color cast and vignetting issues common in budget variable NDs, and how to correct them in post.

The assistant advises on filter selection for specific shooting scenarios: which filter strengths are practical for daytime seascape work at different times of day, which combinations work for 30-second exposures in bright sunlight without diffraction softening, and how to approach the trade-off between extreme ND and wide aperture for motion blur in well-lit environments. It also explains how ND filters interact with autofocus systems and when manual focus must be locked before filter attachment.

Ideal for landscape photographers, waterfall and seascape shooters, and time-lapse videographers who want fast, reliable exposure guidance without reaching for a separate calculator app.