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a robot in flight joined with the time exposure of its flight path

Cover stories: Making the flapping-wing robot cover

Cover stories offer a look at the process behind the art on the cover: who made it, how it got made, and why.

robot flying upwards with time exposure trailSkopei Films/©TU Delft

The original cover photo submission from Matěj and his research team.

The robot flew across the video screen, twisting and turning in the air just like the fly it was mimicking. Its movements reminded me of how those pesky insects always manage to avoid your swatting hands. The robot’s astonishing agility left me dazzled. How was I going to translate the energy of the video into a single still image worthy of a Science cover?

After reading the Report by Karásek et al. in this week’s issue of Science and watching the supplementary movies, I better understood the impressive abilities of this robot. I then decided on the two most important facets of the cover image: First, movement—it would be important to display the mechanics of the wings flapping and the robot’s unique flight patterns. Second, impact—I needed an image that would capture our readers’ attention. I wanted the robot to seem like it was going to fly off of the page.

To produce initial images and video, Matěj’s team, based in Delft, the Netherlands, worked with Skopei Films, a film production company located in the same city. The first cover photo they proposed was a lovely picture that shows the robot flying upward with a long exposure trail. This photo suggested potential for capturing the mobility and visual impact I envisioned for the cover. In a meeting with Matěj and Max van Boxel, DP/Director at Skopei Films, we discussed my goals for a composition that would more clearly portray the motion of the wings and the flight pattern. Accomplishing these objectives in one multi-exposure photograph presented daunting technical challenges.

Skopei Films/©TU Delft

A camera mounted to a gliding track, with Matěj in the background adjusting the robot setup.

First, having the robot fly toward the camera was not giving Max and his team enough control over photo composition or the angle needed to capture the shape of the robot from the horizontal perspective. The solution was to tether the robot to a tripod and set it to hover in place. Now, instead of the robot approaching the camera, the camera was positioned on a gliding track sliding away from the robot.

Skopei Films/©TU Delft

The flying robot highlighted in blue light during a long exposure take to capture the flight path.

The flapping wings, illuminated by a cool blue light, created lots of variables. The velocity of the wings determined how strong the flapping wave pattern appeared in the trail. With stronger velocities, it became choppy, similar to the motion of helicopter wings. After a number of tests, we settled on a more delicate, insect-like fluttering pattern that seemed like a better expression of the robot’s inspired design. The overall trail pattern or flight route was also determined by the gliding of the camera. After a number of trials, we achieved a flight pattern that ended with an elegant curl, thus creating the feeling that the robot is accomplishing one of its extraordinary turns at that moment.

Capturing the robot’s body and moving wings took more experimentation. Max and his team had to find an exposure time slow enough to capture blur on the edges of the wings but also fast enough to keep the robot body in sharp focus. To show all four wings opened in the shape of an “X,” the timing had to be perfect.

Skopei Films/©TU Delft

The robot secured to a tripod, allowing the photographer to have more control over composition and timing of all four wings in motion.

Trying to solve all of these problems proved an enormous challenge. In a perfect world, this would have been accomplished in a single multi-exposure photograph. But as each problem was solved, new ones emerged. For example, we used a tripod to correctly position the robot, but this apparatus ended up blocking the space needed to create the long exposure trail. Furthermore, the use of a strobe light created the desired highlights on the body and wings but resulted in the robot appearing to be frozen in mid-air, with no motion blurring the wings.

Eventually, we determined that the only way to show all of the needed elements was to create them in two separate exposures, which we then combined. One photo depicts the complicated capture of the robot in flight, and the other shows the long time exposure of the blue-shaded flight path. Joined together, these images portray both the remarkable mechanical functions and the amazing agility of this elegantly engineered device.

Skopei Films/©TU Delft

The final cover, showing the robot in flight joined with the time exposure of its flight path.

When it comes to creating composite imagery, both Bill Douthitt, Science’s Photography Managing Editor, and I adhere to a simple rule: Don’t do it. The last thing we want is for our readers to doubt whether a picture is real or to question the veracity of the photos in Science. However, this was a very unusual situation. These two exposures are real photographs of the same movement of the same robot. Technical and physical limitations obstructed our ability to the capture the desired result in a single multi-exposure image.

Ultimately, I trusted that Matěj understands what his robot can and cannot do. The established working relationship between Matěj and Max was a blessing. I loved having the researcher, who knows his work best, collaborate with the visual artist during the creative photographic process. It was a rare opportunity to have such a productive relationship between a scientist and a visual artist. I hope it’s something I come across more often in future assignments.

Emily Petersen is a Photo Editor at Science.