Filming Push: Reducing the flickering of Pads

Background

To enable Push to show different colors and shades, the Pads are lit with sets of RGB LEDs. Since LEDs can only be on or off, difference in luminosity is achieved through modulating the frequency with which the LEDs are flickering. This is not visible to the human eye. When pointing a camera at Push, however, the flickering becomes visible.

Technical solution

To get flicker free results when using Push, one needs to sync the shutter speed of the camera with around ⅓, ½ or the native amount of the Pushs LEDs flickering. Push’s LEDs are on a 106.8 Hz refresh cycle, so the working numbers are:

35.5 Hz, 53.0 Hz, 106.8 Hz

Even if you can’t set up your camera to meet these exact numbers, you usually can get working results in a close range of these numbers - for example, values between 35Hz and 36Hz might work fine with your camera and unit, if you can’t set up your camera to 35.5Hz. We recommend using your camera display for reference.

Camera choice and settings

A freely adjustable shutter speed is not too common on consumer video cameras today. Most cameras offer a variety of speeds (e.g. 12.5Hz, 25Hz, 50Hz,100Hz), which is not close enough to what is needed with Push. Webcams, Photo cameras or cameras in mobile devices won’t work either. There is a large range of semi-pro/pro cameras with finer shutter speed adjustments, available through rental shops for reasonable prices.

Unfortunately, there is no unified name for the technology we’re looking for. So here’s an overview of the features to look for and some recommended cameras:

Canon video cameras

On Canon cameras the feature is called “Clear Scan”. You can find it in most semi-pro camcorders, or pro cameras. We have worked with these, with good results:

Canon XF105, Canon C100, Canon C300

Sony video cameras

The feature is called “ESC” on Sony cameras, and is available on most of their current semi-pro and pro cameras. These have worked for us:

Sony EX1, Sony EX3

DSLRs

We are not aware of any DSLR that has a freely adjustable shutter out of the box. However, there is a thread in the magic lantern community, which might come to a workable result for Canon’s 60D, 6D and 5D MIII soon.

Example movie

This movie was shot on Sony EX3 with a 35.5Hz shutter speed: