We understand the optimal reading distance to be the distance & angle between the viewer and the clock that guarantees the best possible reading. The person should therefore be able to read the hands or shapes without difficulty. The optimal reading distance is a variable value. This value should only be used as an aid when selecting a clock display diameter or character size.
Determining the optimal reading distance requires a suitable starting position. This starting position can be altered by several factors. The following 5 points could influences the optimal reading distance of a time display:
🔢 Size & Shapes of the time display – The numerals are usually slightly easier to perceive. However, the difference between numerals and line marks is not extraordinary. What is important here is the size of the display diameters & hands in case of analog clock or character height in case of a digital display clock.
📐 Viewing angle of the clock – The clock must be positioned correctly & adequately to give a clear viewing angle. If you only see the clock from the sides, the optimal reading distance may be reduced. . Weak lighting can cause the reading distance to be reduced. Make sure that the LED luminosity can be adjusted if desired.
🎇 Light sources – Sunlight can influence the reading distance. Excessive light can cause general vision to deteriorate. So if you install a clock in a room or place, think about the direction from which the light sources are coming.
🤓 The personal visual acuity – If a person has a Low vision, he or she will have a different optimal reading distance. In our calculation, we always assume a normal visual acuity (Visus) of 0.7 – 1.6.