What does an ND filter do?

A neutral density (ND) filter reduces the amount of light entering the lens without changing the color. This forces a longer shutter speed or wider aperture, enabling motion blur in bright conditions or creative exposure control.

How many stops is an ND64 filter?

An ND64 filter is 6 stops. The relationship is stops = log2(ND factor), so ND64 = log2(64) = 6 stops. Each stop doubles the required shutter time.

What is optical density (OD)?

Optical density is another way to rate ND filters: OD = log10(ND factor). An ND64 filter has OD 1.8 (log10(64) ≈ 1.8). OD values appear on many Lee and Cokin filters.

Can I add two ND filters together?

Yes — stacked filters add their stop values. An ND8 (3 stops) stacked with an ND64 (6 stops) equals 9 stops total, equivalent to an ND512.

My camera only goes to 30 seconds — what do I do?

Use Bulb mode with a cable release or remote shutter trigger. Set the camera to Bulb, open the shutter, and close it manually after the calculated exposure time elapses.

Does the ND filter affect aperture or ISO?

No — this calculator only adjusts shutter speed. Aperture and ISO stay the same as your metered settings. If you want to change depth of field or ISO too, account for those changes separately.

ND Filter Exposure Calculator

Name: ND Filter Exposure Calculator
Availability: InStock
Author: Nham Vu

Enter your base shutter speed and ND filter strength to instantly calculate the new exposure time needed after adding the filter.

Base Exposure (No Filter)

Base Shutter Speed

Filter Specified As

Stops ND Factor Optical Density

Filter Strength (Stops)

Adjusted Exposure

Fill in the inputs and click Calculate.

Stack a Second Filter

Add a second ND filter on top of the first and recalculate.

Second Filter (Stops)

Stacked Result

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Common ND Filters Reference

Stops, ND factor, and optical density for standard filters.

Filter Name	Stops	ND Factor	OD	Light passed

Summary

Enter your base shutter speed and ND filter strength to instantly calculate the new exposure time needed after adding the filter.

How it works

Meter the scene without the ND filter and note the shutter speed.
Enter that base shutter speed using the selector or the custom input.
Select the ND filter strength in stops (e.g. 6 stops) or by ND factor (e.g. ND64).
The calculator multiplies the base shutter time by 2^stops to get the new exposure.
Read the adjusted shutter speed — use it on your camera or remote timer.

Use cases

Calculate long exposures for silky waterfall and river shots.
Find the correct shutter speed for smooth ocean or sea shots in bright sunlight.
Convert ND factor to stops or stops to ND factor for unfamiliar filters.
Plan exposures exceeding 30 seconds that require a remote shutter release.
Stack two ND filters and quickly compute the combined new exposure time.
Verify filter math when switching between stop-labeled and factor-labeled filters.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu