If you use flash in your photography, you might have heard of the term ghosting. What is it, and is it bad? I just got back from two weeks of photographing hummingbirds using flash, and ghosting showed up a few times. Let’s look at what it is, and is it bad?
When you photograph in available light outdoors, the sun is your one source of light. If you want to freeze action, you just keep increasing your shutter speed until the movement is stopped. But hummingbirds present a special challenge. Because their wing beats are 60 beats a second and faster, even 1/8000 shutter sometimes doesn’t freeze their wings (if you want to freeze the movement…maybe you don’t!). To solve this challenge, we light the hummingbirds with flash. If flash is the only thing illuminating the hummingbird, then flash duration will freeze the movement, not shutter speed. We were setting our cameras to F16, ISO 100 and 1/250 of a second…which basically produced a black photo unless the flash went off.
But here is the challenge. Look at the image at top. This bird was illuminated both by flash and ambient light. I used a slow shutter speed to bring in the background, and flash to freeze the wings. But did it work? Not really. The flash froze and rendered the wings when it popped off, but the slow shutter speed allowed ambient light to burn in and capture wing movement in the bird. The result is ghosting…both the flash and ambient light render the scene, resulting in a double exposure look in the final shot. If I illuminated the background with flash (or used a cardboard background and lit it with flash), then no ghosting would occur.
So all ghosting is bad? Absolutely not! Actually ghosting helps me create creative commercial images on assignments all the time. In the image above, speed lights froze scene while ghosting was creating with camera movement during a long exposure. As with so many things in photography, ghosting can be good or bad, it just depends on what you want in your final image.