FAQ: Why can't I calibrate the edges / corners of my screen?

[Dan]

If you are having trouble calibrating the edges or corners of your screen, the problem is most likely related to a "sub-optimal arrangement" of the screen, the participant, and the camera. This is particularly common with the top corners because the participant's eye movement may extend beyond the camera's trackable range. Most EyeLink setups trackable range of ~32° x 25°, with the exception of the Tower Mount which has a trackable range of about 60° x 40°. If the screen is places too close to the subject or the camera is not optimally placed between the subject and screen then you will have difficulty getting a good or usable calibration. Please see the following thread for further details about the trackable range:

What is the Trackable Range and why is it important?

To overcome these problems, please verify the following:

• Make sure that the calibrated area of the Display monitor is within the trackable range of your EyeLink system. Our online Trackable Range Calculator is a very useful tool in this respect.
  • The EyeLink system's trackable range is 32° x 25° for all systems with the exception of the Tower Mount which has a trackable range of about 60° x 40°.
    
  • For the Desktop mount, a quick and simple rule to find the minimum viewing distance for the Display monitor is to multiply the width of the screen, in millimeters, by 1.75. The result should roughly be the distance that the Display monitor needs to be from the participant's eyes for the entire Display monitor to be within the trackable range. So a standard 22" Monitor which is approximately 50cm wide would need to be at least 88 cm from the participant's eyes.
    
• Make sure that the camera placement relative to the participant position is correct. The images below illustrate the proper camera placements for various systems. Please note the images on the right side - when looking at the monitor from the participant's perspective there should be no visible "gap" between the bottom of the monitor and the top of the camera:
  

EyeLink Portable Duo
   

EyeLink 1000 Plus
   

EyeLink 1000
   

If you continue to have issues after making the adjustments above, please contact support@sr-research.com and provide a short video showing the entire Host PC screen during Camera Setup and Calibration/Validation which illustrates your issues along with a photo of the physical setup of the equipment so we can help you understand the nature of the problem.