Materials: ∙ Empty 20- or 24-oz. aluminum can ∙ 6-cm. disc (cut from black card stock) ∙ 25-by-7–cm. strip (cut from black card stock, with 1-cm. notches on one long side) ∙ Roll of black gaffer tape ∙ 8-by-5–in. sheet of semimatte photo paper (i.e., half of an 8-by-10–in. sheet) ∙ Plastic cable ties Tools: Can opener, pin, scissors, red light, blow-dryer, computer, flatbed scanner
- Remove the can’s top with a can opener, and poke the middle of its side with a pin. Next, cut out the disc and notched strip from the black card stock.
- Wrap the strip around the can’s base, and bend the notches inward at a 90-degree angle. Tape the disc on top of the notches to form a removable black lid.
- Move everything into a darkened room. Turn on the red light to see, and insert 1⁄2 sheet of photo paper into the can facing the pinhole. Put tape over the pinhole.
- Tape the lid over the can’s open end, and secure it with gaffer tape. (Use plenty of tape to ensure the camera is light-tight and waterproof.)
- Take the project outside, aim the pinhole toward the southern sky, and vertically fasten the can to a signpost with cable ties. Uncover the pinhole.
- Wait a month to a year (the longer the exposure, the more solar tracks appear). After the wait is over, cover the pinhole and take the camera indoors.
- Remove the lid, and blow-dry the photo. Place it on a flatbed scanner, and make one-—and only one—high-resolution scan. (Don’t do a preview scan!)
- Open the image, enhance its contrast (e.g., via “auto-equalize” or “auto-levels” commands), and invert the colors. Save the image to your computer. Approximate time to build this project: 15 minutes Cost: Less than $1 per photo Difficulty: 1/5 April 27, 2014: Worldwide Pinhole Photography Day (for details visit pinholeday.org) **Email your solar graph scans to **manual@popsci.com WARNING: __Wear protective gloves when cutting beer cans. Also mind the law; strapping up empty cans in __public may be viewed as littering—__or worse. This article originally appeared in the April 2014 issue of Popular Science.