ND Filter Calculator
Enter your shutter speed without the filter, select your ND filter strength, and see exactly how long your exposure needs to be. Essential for long exposure photography with neutral density filters.
All Filters at This Shutter Speed
Starting from , here's what each ND filter gives you.
| Filter | Stops | New Shutter | Good For |
|---|---|---|---|
Understanding ND Filters
An ND (neutral density) filter is basically sunglasses for your camera. It's a dark piece of glass that sits in front of your lens and blocks light, without shifting colours.
Why would you want less light? Because it lets you use much slower shutter speeds, even in bright conditions. That's how you get silky waterfalls, streaking clouds, and dreamy motion blur in the middle of the day. They are one of the most important tools in landscape photography.
Why Use an ND Filter?
Try shooting a long exposure in daylight without one. Your image will be completely blown out. Even stopped down to f/22 at ISO 100, a sunny scene might only give you 1/30s or faster.
Now slap on an ND1000 (10-stop) filter. That cuts light by a factor of 1,000, turning 1/30s into a 30-second exposure. Choppy ocean waves become a smooth glass surface. That's the magic.
ND Filter Naming: Stops, Numbers, and Optical Density
This is where ND filters get unnecessarily confusing. There are three different naming systems, and manufacturers mix them freely.
The "stops" system is the most intuitive. A 3-stop filter reduces light by 3 stops (8x darker). Simple enough.
The "ND number" system tells you the multiplication factor. ND8 means it lets through 1/8th of the light. Same as 3 stops, just a different label.
Then there's "optical density", which uses decimals. ND 0.9 equals 0.9 optical density, which is also 3 stops. This calculator shows all three formats so you can match whatever your filter says on the box.
Which ND Filter Should You Buy?
If you're starting out, grab two: a 6-stop (ND64) and a 10-stop (ND1000). Those two cover almost everything.
The 6-stop is your everyday workhorse. It smooths water nicely and adds subtle motion blur without pushing you into multi-minute exposures. The 10-stop is for when you want the dramatic stuff: mirror-flat water, clouds streaking across the sky.
You can also stack filters for even heavier light reduction. A 6-stop plus a 10-stop gives you 16 stops total, turning a 1/125s exposure into nearly 9 minutes. Just watch for vignetting when stacking, especially on wide-angle lenses.
Tips for Long Exposure Photography
Use a sturdy tripod. This is non-negotiable. Even tiny vibrations during a multi-second exposure will ruin your shot. A remote shutter release or your camera's self-timer helps avoid shake from pressing the button.
Compose and focus before you attach the filter. With a 10-stop ND on, your viewfinder goes almost black. Autofocus won't lock on anything. Get your shot set up, switch to manual focus, then screw on the filter.
If your calculated exposure goes beyond 30 seconds, you'll need Bulb mode and a way to time it yourself. That's exactly where this calculator earns its keep.