Boris Homiakov's One-Pixel Camera Takes Eight-Hour Exposures — "Developed" in a Spreadsheet

Maker Boris Homiakov has built just about the simplest digital camera you can think of, using a photoresistor as an image sensor — capturing pictures one pixel at a time.

"In typical consumer cameras, each pixel of the photograph uses three such elements, each with a color filter that restricts light detection to a narrow spectral band (red, green, blue)," Homiakov explains of the project. "But what if we use only one light‑sensitive element (a future single pixel) and obtain a photograph by moving this element along two axes while recording the brightness value at each point of the future image? Effectively, this would be a primitive scanner. We just need to project the future photograph onto a virtual plane (as in a conventional camera)."

The complexities of modern image sensors are entirely ignored for Homiakov's creation, which uses instead a simple photoresistor — a basic component that varies its resistance according to the amount of light which lands on it. They're typically used to adjust the brightness of an electronic light according to ambient conditions, but in Homiakov's camera it forms an image sensor — recording the brightness it receives that can then be turned into one pixel of a planned image.

A pair of stepper motors linked to an Arduino UNO microcontroller board turn that single pixel into multiple, moving the photoresistor horizontally and capturing individual readings at set points — then shifting everything vertically to start again. The readings are captured in a spreadsheet, with a conditional formula that shades the cells according to the brightness recorded. The result: a 221×186-pixel bitmap "image" — captured through a magnifying-glass lens over an eight-hour period.

"The dark streaks indicate that the sun was obscured by a cloud at these moments," Homiakov notes, "meaning the light flux is significantly lower than in direct sunlight. The problem of dark streaks can be solved by adding a +1 photoresistor to the camera, which will record changes in the overall illumination. Then, taking both readings into account, a more even image should be obtained."

The project is documented in Russian on Homiakov's blog, with an English translation available on Hackaday.io.