Which filters would be useful for long exposure photography?

Question

I'm a beginner hobbyist who wants to take long exposure shots of lightning, fireworks, the beach, etc., during both daytime and night time. I would also love to take shots like this. So basically everything from 5 second exposures to 5 minute ones.

I know very little about filters or which ones are "must haves". I've read that you need ND filters especially if you're doing long exposures or want to get a "silky water" effect when the sun is out.

At the moment, I have a Nikon Z6 and a tripod, and a 24mm lens (72mm diameter) and a 50mm lens (62mm diameter). I know that step-down rings exist but they can result in vignetting. I'm not sure if there are any cons to using step-up rings but presumably I can't use a lens hood then.

Alternatively, I could just get a dedicated ND filter for my 24mm lens and use the other lenses without filters, particularly because I'd mainly do long exposures of landscapes with the 24mm, but I don't know yet since I'm still new to this. I've been looking at this NiSi ND kit in particular.

I don't really have a budget, but ideally I'd want filters that only negligibly reduce image quality but are still reasonably priced. Where does the point of diminishing returns start to kick in for ND filters?

Answer 1

There are two kinds of actually useful ND filters, although I'm sure you can find an ND filter with any stop count you want.

One is usually about 16x or 4-stop filter. These are intended for flash photography outdoors in daylight when used with a fast lens. Without flash, in these conditions you would be using a fast exposure time such as 1/8000 to allow using fast lens wide open, but flash sync speed of common shutters are around 1/200 seconds so that won't work without high speed sync flash. It's possible to use a flash that has high speed sync, though. If for example you use 1/3200 second exposure time, this means 1/16 of the shutter is open at a time. High speed sync works by continually feeding bit of power to the flash. The capacitor from which the power is supplied has a limited size. So if 1/16 of the shutter is open at a time, you get only 1/16 of your flash power. Same is true with a 16x 4-stop ND filter: it lets only 1/16 of the flash light through.

My opinion is that if you have the option to use high speed sync, it makes these 16x 4-stop ND filters obsolete.

Another is usually 500x or 1000x, 9-stop or 10-stop filter. These are intended for long exposure photography during daylight hours. A 16x filter wouldn't give you long enough exposure times during sunlight to photograph flowing water in a smooth way. That's why these ND filters let only very minimal amount of light through, only 1/500 or 1/1000 of the light in the scene.

Get a 9 or 10 stop filter. That's what you want for your use case.

With fireworks you probably don't need ND filters though. Fireworks are shot at night, and the fireworks themselves work as the "virtual shutter". Point a camera at fireworks, begin exposure, the fireworks perfectly well expose the sensor with no extra filters required.

For lightning night time you may be able to do without an ND filter, the lightning bolt will be overexposed but that's probably necessary in any case. Daytime lightning, you want to stretch the exposure time as long as you can to maximize your chance of capturing lightning so that's why ND filter with as many stops as you can find (meaning 9-stop or 10-stop filter) is useful or else you'll overexpose the background with exposure times where you maximize your chance of capturing lightning.

Answer 2

My advice is to buy an inexpensive square filter set and get some experience using it (or discover that long exposure photography turns out not to engage you long term).

Square filters can be stacked and graduated (and maybe color) filters are also useful in many situations.

Starting out, cheap filters are less likely to be the limiting factor in your photography. Usually it is the grunt work of setting up a tripod in the dark, or rain, or wind, or cold (or all four) that will limit what you make.

To put it another way, the most likely image quality issue will be not making an image at all because it seems like too much trouble.

Only with experience you will know what works for you…and more importantly what doesn’t. Not just in terms of filters. In a year you may prefer different lenses with different sizes filter threads.

Only with practice will you become less likely to drop a filter while changing it. Less likely to set a filter down and drive away. Less likely to smudge and scratch its surface.

The best filters are the ones you have with you.

Answer 3

Another use case than in juhist's answer is to make a long enough exposure to do intentional camera movement. You can move the camera or zoom the lens during the exposure. That takes exposures of at least 1/10 second or so and I prefer 1/2 or 1 second so I am not in a hurry. You can also pan to follow a moving subject while blurring the background. Again you want 1/10 second or so. I find an 8x or 3 stop filter gets me in the range I want in bright sunlight using ISO 100 and the minimum aperture on my lens.