Why do computer screens flicker on camera?

Computer screens flicker on camera because the camera and the screen are running on different timing cycles that don’t stay in sync. Your screen refreshes the entire image dozens or hundreds of times per second, and your camera captures the image by reading its sensor row by row. When those two cycles drift out of phase, the camera catches the screen mid-refresh, and the result is horizontal bands, rolling lines, or a pulsing flicker that you can see in the recording.

To understand why, it helps to know how each side works:

How a screen refreshes. A modern LCD or OLED monitor displays an image by lighting up the pixels row by row, top to bottom, in a sweep called the refresh cycle. A 60Hz monitor does this 60 times per second; a 120Hz monitor does it 120 times; a 240Hz gaming monitor does it 240 times. Between refreshes there is a brief dark period when the pixels are transitioning. To your eyes, the screen looks stable because your visual system integrates the rapid updates into a continuous image.

How a rolling-shutter camera captures. Most digital cameras — phones, DSLRs, mirrorless cameras — use a CMOS sensor that reads out one row of pixels at a time, then the next, then the next. This is called a rolling shutter because the exposure “rolls” down the sensor. A few specialized cameras (some cinema cameras, machine-vision cameras) use a global shutter that captures the entire sensor at once, but those are expensive and uncommon.

Why the two interact badly. When the camera’s rolling shutter reads row 1 of the sensor, the screen might be partway through a refresh cycle, so row 1 sees the screen at moment A. When the camera reads row 100, the screen has moved to moment B. If the screen is brighter at moment A than at moment B, you get a horizontal band in the recorded video. If the screen is showing different content at moments A and B (because of scrolling, animation, or video playback), you get a sheared, Jell-O-like distortion.

The classic visible result is a horizontal dark band that moves up or down the recording. The band moves because the camera’s rolling shutter is sampling at a slightly different rate than the screen’s refresh, so the phase relationship between the two drifts over time. Sometimes the two cycles sync up momentarily and the flicker disappears; then they drift apart and the band reappears. This is why some recordings of computer screens look fine for a few seconds and then suddenly look terrible.

Three factors that make it worse or better:

• Higher refresh rates help. A 240Hz screen refreshing four times as fast as a 60Hz screen makes it more likely the camera will sample at least one bright moment per row. The flicker doesn’t disappear, but it’s less visible.
• Shutter speed matters more than frame rate. A faster shutter speed captures a smaller time window, which means each row captures less of the refresh cycle’s variation. The ProVideo Coalition piece notes that the “fix” is usually a faster shutter speed, not a higher frame rate.
• Global-shutter cameras eliminate the artifact. If you’re recording a screen professionally and the flicker matters, a global-shutter camera is the only real solution.

Practical fixes when recording a screen:

• Match shutter speed to refresh rate. If the screen is 60Hz, try a shutter speed of 1/60 or 1/120 (which divides evenly into the refresh cycle). This doesn’t always eliminate the flicker but often reduces it.
• Use a faster refresh rate. If you can set the screen to 120Hz or higher before recording, the artifact becomes less visible.
• Use an external recording tool that handles the conversion. Screen-recording software that captures the digital output (HDMI or DisplayPort capture cards) does not run into the rolling-shutter problem because it captures the digital signal directly, not through the camera’s sensor.

The artifact is not a bug in the camera or the screen — it is a predictable consequence of two unsynchronized timing systems. The same physics is why old CRT TVs flickered visibly when filmed, and why filming computer screens in movies has required specialized equipment for decades. Modern cameras and screens have made it less common, but the underlying timing issue is unchanged.