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 (mandatory)
Use the plastic-card method; or measure and enter the length of the blue ruler on the Settings screen (in millimeters). This is automatically saved and needs only to be repeated when changing screens or resolution.
Important: After calibration, don’t change the zoom level of your operating system or the browser! Best re-check with the plastic card – you can detect zoom changes of ×1.5 at one glance.
Distance observer–screen (mandatory)
Enter in Settings (in centimeters, but there’s a conversion to inch), and be sure it’s large enough to avoid ceiling effects, see the Manual (FrACT₁₀ or FrACTclassic-PDF) on this. “max possible acuity” / “min possible LogMAR” must be better than your desired best acuity. This setting is automatically saved.
Luminance of the visual display unit (mandatory)
DIN and ISO norms prescribe the range 80–320 cd/m², easy to achieve with current display units; most cases: set to maximum.
Luminance of the surround (mandatory)
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 (optional for acuity, mandatory for contrast)
- For acuity: not very important. Ignore, or
- in FrACT₁₀ go to Settings>Gamma and use the ± buttons
- in FrACTclassic go to Settings>Luminance linearisation and use the top two buttons
- For Vernier: semi-important. Perform the simple calibration above
- For contrast thresholds: very important. Best to use a screen calibrator (these have become very afforadble, e.g. Datacolor’s Spyder, but must be the “Elite” or better version), calibrate the screen to a gamma=1.0, and enter that gamma value of 1.0:
- FrACT₁₀: Settings>Gamma; use the ± buttons or enter directly
- in Fractclassic Settings>Luminance linearisation>gamma value
- You can also use a screen calibrator to set the system to another gamma value (e.g. 1.0); if so, then enter that value in FrACT’s gamma box.
- This setting is automatically saved by FrACT.
Semiautomatic export of results → spreadsheet (optional)
- Select the correct decimal mark (comma or period) for your locality in Settings, bottom right. (Important, otherwise the spreadsheet might interprete your results as dates!). In FrACT₁₀ the default is “automatic”, that should be sufficient.
- Decide whether you only want the final result or the full history (with reaction times etc.) and select in Settings
- Start the spreadsheet program (e.g. Excel, LibreOffice, or Numbers) beforehand, add additional information you might want, and switch between FrACT and spreadsheet with the task-switcher shortcut (⌘-tab for Macs, alt-tab for Windows)
- After each test run, switch to the spreadsheet and paste. Voilá!
More export options in the FrACT₁₀ Manual.
Remote keypad for response entry (suggestion)
- This proved very useful!
- If you are using a remote keypad for response entry, make sure it is oriented correctly :). Really.
Switch off keyboard repeat (suggestion)
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 (suggestion)
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.
RTFM
Much more detail here: FrACT₁₀ Manual or FrACTclassic Manual [PDF].