Use the plastic-card method; or measure and enter the length of the blue ruler in Settings>General
(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! (Or recalibrate) Best re-check with the plastic card – you can detect zoom changes of ×1.5 at one glance.
Enter in Settings>General
(in centimeters, there’s a conversion to inch). It must be large enough to avoid ceiling effects, see the Manual on this. “max possible acuity” ≙ “min possible LogMAR” must be better than your desired best acuity. This setting is automatically saved.
DIN and ISO norms prescribe the range 80–320 cd/m² (recommended: 200 cd/m²). This is easy to achieve with current display units; most cases: set to near maximum, keeping black black.
No light sources or reflective surfaces seen by the testee should be brighter than the visual display unit. No glare sources (e.g. spotlight, light reflex, any very bright surface) should be within the field of view.
SettingsGamma
and use the ± buttons as explained there.Settings>Gamma
.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.
This avoids unwanted responses, caused by prolonged pressing of a key. Use your operating system’s keyboard options to do this.
Settings>General
, bottom left. (Important, otherwise the spreadsheet might interprete your results as dates!). In FrACT₁₀ the default is “automatic”, that should be sufficient.Settings>General
.More export options in the FrACT₁₀ Manual.
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 FrACTclassic Manual [PDF].