I have added a new way to size-calibrate FrACT₁₀. For correct acuity assessments, FrACT needs to know the screen resolution (size of a pixel in degrees) and the observer distance. Screen resolution is measured by entering the length, measured in mm, of a “blue ruler line” in Settings. Now you can click the button kindly named Use Credit Card instead. The image of a credit card appears, you place a real one on top of it and click buttons until virtual and real realities agree. [No money will be deducted from your account.]

This is not only easier, but also caters for “imperial measures”. One still has to enter the observer distance in centimeters, should I add a feet option?

A few more details are in the manual. I’d love to hear feedback, if it works for you, and how the GUI might be improved.

Happy acuities!