[groby_b]

Eyes usually look at diffusely reflected light, which has a different impact than direct light.

A white reflective surface (whiteboard) in direct sunlight is 1.6cd/cm^2. Consumer monitors are ~300cd/cm^2

(I'm not sure how much bearing this actually has on eye health, this is just to illustrate how looking at a monitor and at a piece of paper is significantly different)

[Cerium]

I think there is a unit error here. I believe that sunlight on white paper is about 1.6cd/cm^2, while consumer monitors are about 300cd/m^2 (meter not cm). Essentially, you want the brightness to match the environment.

http://www.infocomm.org/filestore/display_specs_and_human_vi...

[groby_b]

There is indeed. Oops. I'd delete - no point polluting the Internet with more bad info - but time window has expired.

Thank you for the correction!

[lukevp]

Your units are wrong. Monitor brightness is measured in square meters not square centimeters. A square centimeter is 10,000 times smaller than a square meter.

[beervirus]

As noted, your units are wrong. A white reflective surface in sunlight is FAR brighter than a computer monitor.

[yoz-y]

Hm, to be honest I find reading a book is direct sunlight quite more challenging than staring at a screen, because the reflected light is quite unbearable.

[TremendousJudge]

>A white reflective surface (whiteboard) in direct sunlight is 1.6cd/cm^2. Consumer monitors are ~300cd/cm^2

Why does it hurt my eyes to look outside after a while looking at a screen in a well lit room? (the sun is not directly visible, just buildings, trees and sky)

[atomicnumber3]

Because the sun is an enormous sphere of hydrogen-helium plasma with a core that's undergoing fusion just due to gravity. Even indirect sunlight is still a very large amount of light and energy.

I don't mean to sound flippant, but I think sometimes people forget just how insanely energetic stars of all sizes are.

[TremendousJudge]

But GP's point was that a screen is much brighter than a sunlit surface. You can't both be right, or I'm missing something.

[gowld]

cd/m^2, not cd/cm^2

I don't understand. Monitors are intended to be set to the same brightness as the ambient environment. 300cd/cm^2 is max, not average.

Of course shining a monitor in your face at maximum brightness is bad, just like staring at a light bulb all day is bad.

[greenshackle2]

You've got your units wrong. Very obviously so, to anyone who has ever taken a laptop outside in daytime.