How did I do that? Lightning Bugs (Fireflies)

Lightning bugsLightning bugs in late spring over a meadow in Central Kentucky

Every once in awhile I will be letting you in on my little secrets. Today I will tell you how I did The Photo of the Day – Lightning Bugs.

They came out early this spring. I first noticed some about a week ago, and last night turned out perfect for the shoot, the air was clear and perfectly still. No wind at all. The only thing I was concerned about – light from crescent moon. Originally I wanted to have totally dark sky with a bunch of stars but it turned out I could use the crescent to my advantage.

For the location I chose my neighbor’s backyard which backs up to the very tip of our lake. There is a meadow with some tall grass and bushes on the other side – that’s where the action was. There was also a dock and a tree in front of me – a nice foreground and good subjects for some light painting. Might as well, right?

The gear:

1. First and foremost – a sturdy tripod. Mine is carbon fiber Induro – a nice alternative to much more expensive Gitzo. It’s been my trusted companion for the last 6 years or so and indeed endured some very harsh environments.
2. My tripod is outfitted with BH-40 ball head from Really Right Stuff. It’s also Really Expensive Stuff but when I upgraded to it from much more economical Manfrotto I never looked back.
3. On top of all this sits my Canon 5D Mark II with 16-35mm f/2.8 L lens. In this project I will be pushing the limits of this wonderful piece of glass.
4. I also use a remote shutter release whenever I set the camera on the tripod. It just makes sense – you don’t want to shake the whole rig when pressing the shutter button. I also brought with me a powerful flashlight for light painting. That’s about it.

In the Field

Lightning bugs don’t emit much light. It’s visible to our eyes (and most importantly to the bug of the opposite sex), but the camera sensor struggles to register it. I took several 2-2.5 min. exposures at f/8 and ISO 200 to do my light painting. I painted the dock, the grass in front of the camera and the edge of the grass on the opposite side of the lake. I could see star trails in the sky but only light trails of bugs flying close to the camera were visible. The meadow was totally dark.

On to the next step. I decided to try the same technique as they use for photographing stars. If you want the stars appear as dots in the sky (as opposed to light streaks or trails) you need to take into consideration the focal length of the lens and the latitude of the star field in the sky (if you want to be very precise). A simplified rule says that your shutter speed can’t be longer than 600/FL, FL=focal length. In other words, if I’m shooting with 16 mm lens my shutter speed should be under 37.5 seconds (600/16). It is not very long for night time. This means you have to use high ISO and have your lens aperture wide open – hence f/2.8.

I made several test shots and found satisfactorily results with ISO 1600, f/2.8 and shutter speed 15 sec. I could see the stars in the sky and lightning bugs in the meadow. I took 10 exposures in rapid succession with these settings to be combined (or stacked) later in Photoshop. Now I have my lightning bugs and starry sky and also my light painting exposures. Perfect! Now I’ll be taking all this back to my digital darkroom.

Digital Darkroom

I import all the images into Adobe Lightroom (I always shoot in RAW format) and make my normal adjustments – white balance, levels (or tone), clarity and vibrance, curve, noise reduction and lens correction. I also like to play with camera profiles to see what works the best. Camera Landscape yields amazing results sometimes but for this shoot I chose Adobe Standard.

I synchronize the adjustments for 10 shots with the high ISO setting and modify my developing settings slightly for the light painting images that are generally much darker. Now I select 10 shots with lightning bugs and stars (high ISO), right click on them and choose “Edit in -> Open as Layers in Photoshop”. In Photoshop CS5 I change blending mode of each layer, except the last one on the bottom, to Lighten. If you own Photoshop CS6 you can select all layers and change the blending mode all at once. Now I have all the lightning bugs from all 10 exposures combined!

Changing blending mode

Unfortunately the same happened to the stars in the sky, and now I have short star trails. This is not what I want. To remedy the situation I duplicate the top layer, change the blending mode of the copy back to Normal and mask everything but the dark portion of the sky where the star trails are visible. Fortunately the bugs stay fairly close to the ground and I don’t have to worry about losing them. 

Removing star trails

I will use the same technique to stack the resulting image with low ISO light painting images. The lens is sharper at f/8, so the additional benefit here is bringing back some fine details in lighted areas.

For quick reference while processing, here's the highly abbreviated version of the Digital Darkroom steps above:

1. Import images to Lightroom
2. Make desired color and tone corrections/adjustments
3. Select the high ISO shots
4. Right click> Edit in> Open as Layers in Photoshop
5. Change the blending mode to Lighten for all layers except the bottom layer
6. To remove star trails - duplicate top layer
7. Change the blending mode of the copy back to Normal
8. Mask all areas except the darkest part of the sky (where trails are)
9. Image> Flatten> Save

That’s it! If you’re a photographer I hope it inspires you to go and experiment at night. These steps were appropriate for these shooting conditions, but you may have to change strategies, repeat steps, or try different settings for your shoot. If you have questions or need more detail on certain steps, please post them in the comments and I'll be happy to answer them.

If you‘re not into all this technical mumbo-jumbo, just enjoy the view!