Thomas Knoll wasn’t trying to build the world’s most influential image editor. In 1987, the University of Michigan PhD student had a narrower headache. His Macintosh Plus displayed images in black and white only, no grayscale, which made his computer vision research far harder than it needed to be. So he wrote a small utility he called Display. It tricked the screen’s pixels into simulating shades of gray. That piece of student code, scratched out to solve a concrete problem, became the foundation of Adobe Photoshop.
The software first hit store shelves on February 19, 1990. Over the next three and a half decades it reshaped photography, publishing, film, and web design. Thomas Knoll’s own account, drawn from a 2015 interview on the Adobe Blog, supplies the definitive version of events. For a generation that edits images daily without thinking about where the tools originated, the history carries fresh weight.
