Freiburg Vision Test (‘FrACT’)
by Prof. Michael Bach – Checklist

To achieve high-quality results you will have to be knowledgeable in sensory testing and want to observe the following

This is free software. There is no warranty for anything.

Calibration to the screen resolution

Enter the length of the blue ruler on the Settings screen (in millimeters). This is automatically saved by FrACT and needs only to be repeated when changing screens or resolution.

Distance observer–screen

Enter on the Settings screen (in centimeters), and be sure it’s large enough to avoid ceiling effects, see the FrACT₁₀ Manual or classic FrACT3.x Manual [PDF]. “max possible acuity” (decimal units, 1.0=20/20) must be higher than your desired highest acuity. This setting is saved by FrACT.

Luminance of the visual display unit

DIN and ISO norms prescribe a range 80–320 cd/m², easy to achieve with current display units

Luminance of the surround

The surround requirements depend on screen size. If screen ≥ 10°: not darker than 1% of the screen; for smaller screens: between 10% and 25% of screen luminance.

Luminance linearity of your visual display unit
Semiautomatic export of results → spreadsheet

More export options detailed in the FrACT₁₀ Manual

Remote keypad for response entry
Switch off keyboard repeat (optional)

This avoids unwanted responses, caused by prolonged pressing of a key. Use your operating system’s keyboard options to do this.

Start with a binocular training run

Running a binocular training run with your prticipants has proven useful. They can familiarise themselves with the test, and you can explain the “forced choice” situation, e.g.: “use your best guess, even if you don’t see it!” Usually, I don’t even analyse the results of this run.

“Whoops, pressed the wrong key”

When the subject reports “whoops, pressed the wrong key” during the first 3 trials: It’s best to abort by pressing “5” twice and restart this run.


Much more detail here: FrACT₁₀ Manual or classic FrACT3.x Manual [PDF].