Shooting a projection screen to record a PowerPoint presentation is something you maybe required to do. While there are numerous alternatives to shooting the screen, many of us doing video production in Education are forced to shoot the screen on a regular bases. This posses a number of challenges (white balance, exposure, etc). However, I’ve noticed that one problem that can sometimes stump videographers: what to do when the projection is flickering.
Flickering projection is a common problem you’ll encounter whenever you point a camcorder at an image from a DLP projector. You won’t get the same kind of flickering from LCD projectors, as these two types of video projectors have some key differences. LCD projectors continuously projects an image, while DLP projectors use a spinning color wheel to project one color at a time. The color wheel spins so fast that to your eyes it looks like one image. The camera however is not as easily fooled as your eyes.
How do I know when I am shooting a DLP Projector?
While you could try to Google the projector’s model number, the easiest way to know is to look at the projected image through your camera. If you see a flicker through the camera, but not with your naked eye, then it’s a DLP projector. If you see a flicker with your naked eye, then it’s a problem with the projector.
How can I record a DLP Projector without recording the flicker?
All you need to do is to adjust your shutter speed. In my tests, there is no flicker at 1/60. Remember your shutter speed isn’t related to frame rate. If you are filming at 24 frames a second, a 1/60 shutter speed means that each of those frames is exposed to light for 1/60 of a second. If you exposed a frame to light for longer the camera records multiple cycles of the color wheel. And if you exposed a frame to light for less than 1/60 of a second, it would record only part of the color wheel.
What does this look like?
The video below shows the image from a DLP projector at a variety of frame rates. WARNING: the second half of the video features some very intense flickering. Watch at your own risk.