Laboratory of Brain   ProcessES

Video Switcher for Vision Experiments

  1. It can achieve high luminance resolution. Most computer displays have 8-bit luminance resolution which is too coarse for some vision experiments, such as contrast threshold measurement. By sacrificing color display, a video switcher can increase the luminance resolution. This is the same as Pelli-Zhang video attenuator.
  2. It is designed to drive a color monitor. Unlike the Pelli-Zhang's passive resistor network, video switcher is designed to drive a color monitor to show grayscale images, although it canalso drive a monochrome monitor. Most color monitors have better specifications and are less expensive than monochrome monitors.
  3. It can be toggled between normal color and high grayscale display. You can switch between grayscale mode (experiment) and color mode (normal use) by program, and/or a button. With this functionality, single monitor setup is enough for most vision experiments.
  4. It can generate an accurate trigger to synchronize the recording with visual stimulus. This is very useful when you record electrophysiological or fMRI response, or measure reaction time to visual stimulus.


  • Bandwidth: 250 MHz
  • Input and output impedance: 75 W
  • Input and output connectors: VGA
  • Blue to red ratio: ~127
  • Trigger output: ~4 V, 100 us
  • Power supply (box version only):  100 V ~ 230 V AC, 50/60 Hz
  • Special specifications may be available upon user request

Hardware Requirement

The device can be used on any computer with 8-bit color video card with analog output.

Software Requirement

Video switcher does not have special requirement for software. We recommend free Psychtoolbox in MatLab, which implements a convenient and effective way to use the device. We have a demo code showing how to use it in Psychtoolbox.


Video switcher is designed to connect between computer's video card and analog monitor. Connect the input of the switcher to your computer's video port with the supplied cable, and plug the monitor's cable into the switcher's output port. If you need the trigger pulses, connect the BNC output to your recording device with a cable (not supplied). You can download the user manual here.

Some Tips

  • The color display mode does not have high luminance resolution, and it is designed for normal use other than visual stimulus. Remember to switch to the high grayscale mode when displaying visual stimuli, either by calling a function or by pressing the button for the box version.
  • To ensure accurate trigger timing, you must set on the green value only in the display region. For detail information, check the offprint.

Ordering Information

The price is $280 each for switcher box, plus shipping and handling, which is about $35 for one, and $10 each for additional ones. You can make payments by check, wire transfer or credit card via Paypal.

Contact us

If you like to make an order, have question or suggestion about the video switcher, please contact us by email or