Photographing Fireflies (Lightning Bugs)

It’s almost time to get out and shoot one of my favorite nighttime subjects. Fireflies—lightning bugs for you fellow southerners—make exciting photographs, especially when you show them in their environment. Check out this blog post about one technique for shooting fireflies in a jar. Also, if you want to read about fireflies in general, check out this article.

The biggest problem with taking pictures of fireflies is that the flash of light is not very bright. We can see it just fine, but to record it well on our camera sensor, we have to use a high ISO and wide aperture. It’s very important to understand that the shutter speed has nothing to do with how bright the flashes record. When the light is moving, as with star trails, car lights, and firefly flashes, the ISO and aperture control how bright the light will be in the photo. The shutter speed only affects the linear distance of the light. You want to shoot a speed of several seconds so you can be sure to capture the ENTIRE flash, but the brightness of that flash is determined by the aperture and ISO.

The particular ISO, aperture, shutter speed combination you use will depend on the shooting situation. In all cases, you’ll want to shoot with an aperture as wide as the needed depth of field will allow—f/5.6 or wider. If you’re shooting a wide-angle scene, you can probably get enough depth of field at f/4 or maybe even f/2.8. Don’t worry about depth of field with the firefly flashes. Set you focus based on the overall scene. Any flashes that occur very close to the lens will not be sharp, but it probably won’t matter as they’ll be moving anyway, and fuzzy firefly flashes usually look just fine. Typically, you’ll want to use an ISO of at least 3200. Lower ISOs will show some flashes, but they won’t be as bright and the faint ones won’t show at all.

Just as important as the ISO and aperture is the camera-to-subject distance. If the fireflies are far away, they won’t show up well no matter the settings. If they are very close to the camera, as in the photo below of the cabin, they’ll show up well even at ISOs as low as 100.   

After you get the aperture and ISO set, choose the shutter speed based on that combination. If you’re shooting a scene that has other lights in it, or perhaps a twilight sky or stars, you’ll have to use a shutter speed that will give you a proper exposure and that doesn’t blow out anything. With such a big aperture and high ISO, the shutter speed could be fairly short, and may not be long enough to capture the entire duration of the flashes. You can either go with that, and hope for multiple flashes to show up, or you can shoot several exposures and blend them.

If it’s totally dark and there are no other lights in the scene, you can shoot as long a shutter speed as you like from an exposure standpoint. However, noise will be a big issue with long exposures at high ISOs. To capture just the flashes in a dark environment, I like to keep the shutter speed to no more than 15 seconds. If I need more flashes to show up, I simply blend multiple exposures. While long exposures do increase the noise, if you are capturing only the flashes during these exposures and blending those with a scene shot at a shorter speed and lower ISO, the noise probably won’t be an issue. Noise only shows up in the dark parts of the frame, not in the flashes. So when you blend the exposures and use the “Lighten” blend mode to let only the flashes show through, the noise gets left behind.

The following photos illustrate a few different methods for photographing fireflies. Note that all of them employ the technique of stacking multiple frames. I shot the separate frames for each image stack from the same tripod setup and on the same night. While you can certainly blend exposures made at different locations and on different nights, it’s not something I do. And, of course, you don’t have to shoot multiple exposures at all. There are many situations—twilight, for example—in which you can get a good shot of fireflies in a single frame. I have several shots like this, all sitting on hard drives waiting for me to process them. Also, I have a number of locations scouted for shooting single-frame firefly images during this year’s firefly season.  

Fireflies flash at a light-painted waterfall

Fireflies and light-painted cascade

At dusk, I made an exposure using ISO 200 to capture some detail in the forest. Once it got totally dark, I made a second shot of about a minute at ISO 400, and during the exposure I light painted the cascade using a small LED flashlight with a light blue gel filter attached. Then I shot continuous 30-second exposures at ISO 6400 to capture the firefly flashes. After picking about 8 frames for the flashes, I stacked them as layers under the first two in Photoshop, and then changed the blend mode to “Lighten.”

Fireflies and light-painted trees

Fireflies and light-painted trees

The first couple of exposures were f/5.6, ISO 1600, and 30 seconds. During these, I light painted the trees using an LED flashlight with a red gel filter. Then I shot continuous 15-second exposures at ISO 3200 to capture the flashes. This particular location is swamped with fireflies, so it only took a few frames to get this many flashes. As with the above photo, I stacked them as layers under the tree shots, and then changed the blend mode to “Lighten.”

Fireflies and light painting

Fireflies and light painting with red flashlights

I was having a little fun with this one. I set up the camera while it was still light to get the composition just right. After it got dark, I walked back and forth along the trail while wearing a red headlamp and carrying a red flashlight that I was swinging around. The light painting part was about a minute at ISO 200 and f/8. After the light painting, I shot a few 15-second exposures to capture the firefly flashes at ISO 3200 and f/5.6. All of the shots were stacked as layers in Photoshop with the blend mode set to “Lighten.”

Star trails above a cabin with fireflies

Star trails shine above an old cabin with fireflies flashing

With the shutter set to bulb, aperture at f/4, and ISO at 200, I made two separate exposures. One was for the light painting inside the cabin. I attached a yellow gel to an SB800 flash and made several pops from inside the cabin to create the light-throw effect. In the second exposure, I light painted the exterior of the cabin using an LED flashlight. Then I shot 30 4-minute exposures at f/4 and ISO 200 to capture the star trails. After brushing out the sky from the first 2 exposures so it wouldn’t show through on the blend, I stacked all of the frames in Photoshop as layers and changed the blend mode to “Lighten.” The fireflies were flashing all around, so I knew that some would show up in several of the 4-minute exposures I made for the star trails. However, since the ISO was so low, the only flashes that showed up well were the ones that occurred very close to the camera.

Fireflies and fire in chimney

Old chimney with fireflies

This is 18 separate exposures stacked in Photoshop. I set up the camera before dark to get the composition just right. At the end of dusk, I shot a 30-second exposure to capture the sky using ISO 1600 and f/4. Then I shot the “fire.” Not wanting to build a real fire because it would disturb all the critters living in the old abandoned chimney (not to mention that it would be illegal at this location), I set up some sticks and behind them I placed an SB800 flash with a yellow gel. The problem was that without any smoke for the flash to illuminate, I wouldn’t get the look of a real fire. The flash would illuminate the back of the sticks and the inside of the firebox, but it would be harsh and not natural looking. The solution was to place a small smoke bomb in front of the sticks. I fired the flash using a Pocket Wizard radio remote. After shooting the fire, I made several exposures for the light painting, using f/8 and ISO 200. I tried both red and yellow gels on the flashlight, preferring the yellow gel as it worked better with the color of the fire. After the light painting, I shot continuous 15-second exposures at ISO 3200 and f/4 to capture the fireflies. I got about 10 that had some flashes and stacked these with the others in the final composite.

I realize that the multiple-exposure techniques I employed for these shots are not something everyone will want to do. It requires a lot of careful planning and execution, and at least a couple hours of post processing for each image. However, it’s the ONLY way to get a shot like this, so I endure it. Again, you can shoot firefly scenes in a single image if you choose the right setting and time. Twilight works well because you can capture the overall scene in a single shot as long as you don’t have a huge unlit foreground. If you use a wide aperture and high ISO, any fireflies that flash during the exposure will show up.

For the light painting I do, I use the little Rosco gel filter swatches and attach them to the flash or flashlight using a GelGrip™, a filter holder that I designed. I’ll be talking more about this little guy soon.

Enjoy those flashes in the dark!

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