Ideal Reading Light in Footcandles

Having appropriate lighting levels while reading reduces eyestrain. Short-term effects of eyestrain include headache and dry eyes. Long-term effects of eyestrain include a slight increase in the chance of developing myopia (nearsightedness) and wrinkles around the eyes.

The Numbers

• For casual reading, 20--50 foot-candles (215--538 lumens/m2) is the recommended level of light.
  For intensive reading, such as studying, and for older adults, 50--100 foot-candles (540--1076 lumens/m2) is the recommended level of light.

Older Adults

• Older adults need brighter light to read by because parts of the eye become more opaque over time and because the range that the pupil can open and close diminishes over time. Both of these can let less light into the eye.

How to Measure

• Unless there are special circumstances, you should measure the light with the light meter about 78 cm (30.7 in) from the floor.

Light Meters

• Make sure that you use a light meter made to measure light that the human eye perceives, which is light with a wavelength of 500--600 nanometers.

Misconceptions

• A common misconception about reading in low light is that it causes myopia. Studies indicate that genetics is the major factor to determine whether a person becomes myopic and that reading in low light is only a minor factor.