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If you live in a place where they can be found, photographing summer fireflies is an interesting challenge. Like astrophotography, it takes a little more work and patience–but the results can be pretty awesome!

Living in the Virginia piedmont region, we’ve got lots of fireflies this time of year. I’ve been practicing in my backyard and the woods behind my home, but recently I made an excursion to the Pony Pasture Wetlands along the James River in Richmond, which can be a real firefly hotspot. The video up top covers the visit, but I thought I’d also write up a blog post with some more details about the concept and techniques. Come along!

Fireflies or not, the James River Parks are beautiful places, and the Wetlands are no exception. Lots of nice trails through the woods here.

For photographing fireflies, the basics are reasonably simple. Any one flash of a firefly is a point light source of short duration–kinda like a very small photographic strobe. So like working with flash, to capture the fireflies’ light the primary settings are lens aperture and ISO. I’ve found that a fast lens (f/1.8, for example) works well for fireflies at a pretty low ISO, assuming the ambient light is dim. For a slower lens you’ll need to crank the ISO up a bit more. Needless to say, you’re going to want to be in Manual mode for this–in the dim light of evening the camera will want to overexpose if left to its own devices!

In twilight, for the brighter firefly species (like Photinus pyralis, the “Big Dipper” species common around here) a good starting point is f/1.8 and ISO 100 (or even 50 or 64, if your camera goes below 100). At f/2.8, ISO 200 should work well. f/4 would be ISO 400, and so on. Smaller and fainter fireflies would need a higher ISO to register well in your image, of course. Keep in mind that long exposures add to the noise of your image, so you want to keep the ISO as low as possible for the conditions.

So with the starting point of aperture and ISO set, all that’s left is shutter speed, and here you want to go as slow as you can. The slower the shutter, the more likely you are to capture one or more firefly flashes in each frame. If you just want to capture a firefly or two (or are in a spot with LOTS of fireflies), a single frame might be sufficient.

But I find it’s more impressive to stack multiple frames to create a single image with multiple firefly trails–like a time-lapse video, compressed into a single frame. To do that, you need a few things: A sturdy tripod, an intervalometer, and image-stacking software.

The tripod should be obvious–you want multiple frames, identical in every way except for the fireflies themselves. Plus, you’re going for long exposures of at least a second, preferably even 5 or 10 seconds, which definitely calls for a stable platform.

An intervalometer triggers the camera to take a sequence of frames at regular intervals (hence the name), without having to manually press the shutter button every time. Some cameras have an intervalometer built in, but if yours doesn’t you can get a wired external one for reasonably cheap.

And for stacking the images, I’m sure there are plenty of software options, but I’m using Zerene Stacker. Its primary use is for focus stacking of macro images (which increases the depth of field of the final image), but I find its PMax stacking method works quite well for this purpose also. The drawback is that Zerene isn’t free–the standard version is currently $89, though there is a free 30-day trial. You might also try StarStax, which is intended for astrophotography but might work for fireflies too–it’s completely free and doesn’t even have to be installed, making it easy to try.

The window for photographing fireflies each evening is fairly short. As you’ll see in the images below, I arrived around sunset and the ambient light was just too bright even under pretty dense tree cover. I wasn’t getting very slow shutter speeds, so I was missing a lot of firefly flashes in between frames, which was frustrating. Or I’d set up and start shooting, only to find the fireflies had decided to move to a different spot. Still, you can see a few good trails in these shots, and I think they add a little something to the scenery, at least. On the other end, once darkness really sets in you won’t get much background scenery even with long exposures, which can make for less interesting images. The real magic is when it’s dark enough that the fireflies really stand out, but not so dark that you can’t still get a decent amount of background detail.

So here’s the basic process:
1. Find a spot with a number of fireflies and compose the shot, setting your focus point manually (you should disable autofocus once focus is set so the camera doesn’t change or hunt for focus.)
2. Dial in a suitable aperture and ISO. I suggest starting with your lens’ widest aperture, and an ISO appropriate to that. Again, f/1.8 and ISO 100 is a decent starting point.
3. Set your shutter speed to the slowest/longest you can to obtain a slightly underexposed background. You don’t want the background too bright or the fireflies won’t stand out like you want them to. If you can’t get at least 1.0 seconds, you might want to wait for the light to fade a bit more. 2 seconds is okay, 5 seconds or longer are even better.
4. Set the intervalometer to keep firing the shutter until you tell it to stop. I usually take at least 20 frames, more if the firefly activity is a bit more sparse. 20 frames with at least one good flash or trail should make for a good final image.

Then once you get the images back home, comb through to weed out any that were duds, firefly-wise. Stack the rest in your software of choice, and then edit the final image to your taste. Done!

As the light finally faded, I had more luck. The spot below was fairly active, so I was able to capture a pretty good number of frames with lots of firefly action. Most were in the foliage, but I did get a few trails, which I find more interesting.

And finally, this spot was amazingly active–again, most of the fireflies were in the trees and relatively faint, but the sheer quantity really added up, and there were enough in flight for some added interest as well.

I’m not even sure how near the seasonal peak of firefly activity we are, so I think I might have to go back for another try one of these nights. I learn a bit more every time!

I hope this was useful to you if this is something you’d care to try. Drop me a line if you have questions!

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