Shooting a computer screen may sometimes be a problem because of the likely flicker issues that show up on the footage of the screen. This problem is more prevalent when filming an old computer or TV screen, particularly those that use Cathode Ray Tube, or CRT, an older technology that utilizes a vacuum tube with an electron gun and a fluorescent screen. This type of monitor produces images through light emissions from the fluorescent screen. For modern LCD monitors, this is not a problem anymore; this makes filming a computer screen a breeze.
Access the "Control Panel" of your computer. Go to the "Display Settings," then to "Advanced," and then "Monitor." Change your monitor's refresh rate to 60Hz. This refresh rate is based on the electrical current used, the user's preferences and the actual computer's more specific set-up. As a general guide, the higher the refresh rate, the faster the speed of the flicker seen on the footage.
Set your camera for a test shoot. See if the flicker is already minimized to a passable degree. Due to technical differences between the camera and the CRT monitor, it is impossible to completely remove the flicker. However, you can minimize its effect on the footage your are shooting.
Experiment which refresh rate on your monitor works best when filming. Return to your computer's "Control Panel" until you reach the "Monitor" menu. Change your monitor's refresh rate to 90Hz, then 120Hz. See which one works best by making test shoots for each setting. The basic idea is to set the monitor to have a lower refresh rate that is a multiple of the camera's frame rate.
As a technical guide, low-end cameras typically have a frame rate of 30fps (frames per second). This is rounded off from the exact figure 29.98. Some low-end, mid-range and all high-end cameras offer a frame rate of 24fps, which is rounded off from 23.98. Some mid-range and high-end cameras also offer a frame rate option of 60, which is rounded off from 59.94. The rounded off figures are used because a computer screen's frame rate options are always available as whole numbers only. This means that a camera frame rate of 30fps would most likely work best with a computer refresh rate of 60Hz or 90Hz. On the other hand, a camera frame rate of 24fps or 60fps would most likely work well with a computer refresh rate of 120Hz.
If your camera has an image stabilization or a manual shutter speed adjustment feature, using any or both of them can dramatically reduce the presence of a flicker when filming a CRT computer screen. However, due to the numerical differences between the frame rates used by the camera and the refresh rates used by the computer screen, expect that a slight flicker would still be noticeable under the best settings.
Another option is to use a laptop or an LCD monitor for the filming of the computer screen because, unlike CRT monitors, such monitors don’t have any flicker problem.