Fluorescent tubes go through one on-off-on cycle every 1/120 second. Each row of pixels is exposed sequentially, adding up to 1/30 second or four full cycles going from top to bottom. Purple light emitted early in the cycle comes from mercury and short-lived states in the phosphor mixture, and green light emitted late in the cycle comes from a long-lived Tb(3+) state in the phosphor mixture that continues emitting light at 542 nm for several ms after mercury emission turns off.
[OPN 2021 Photo Contest Editors’ Choice]
—Dan Deptuck, CMC Microsystems, Ontario, Canada