The PI-MAX4:1024i-RF camera from Princeton Instruments, Trenton, NJ, is an intensified camera that enables frequency domain measurements for fluorescence lifetime studies. By modulating the gain of its Gen III filmless intensifier at an RF rate between 1—200 MHz, the camera operates as a 2D lock-in amplifier. Each pixel acts as an individual phase-sensitive (lock-in) detector. The camera has 2 independent built-in direct digital synthesizers: one generates the RF to module the intensifier and the other provides a user-controlled RF signal to modulate the illumination. Time resolution is 10 ps, jitter is 35 ps, and the camera is capable of a 1 MHz sustained repetition rate.