Re: Question about light intensity - direct view versus reflection????

But then, why would an arc from a welder 500 feet away irritate the eye when
it radiates in all directions and doesn't appear to significantly light up
surrounding areas?



I understand that 1) the retinal rods and cones have different sensitivities
to different wavelengths 2) there is a difference between lumens and lux and
3) different materials reflect light differently.










"Richard J Kinch" <kinch@xxxxxxxxxxx> wrote in message
news:Xns98C4E670C1F33someconundrum@xxxxxxxxxxxxxxxxx
SoCal writes:

Is there such thing as photon density as perceived by the human eye?
Thanks in advance.

The common understanding of light is naive. To understand the question
you
pose, you must appreciate the difference between areal and angular
densities of luminous flux: luminance vs luminous intensity vs
illuminance.

Consider why Bailey's Beads are comfortable to look at, and the landscape
about you is hardly moonlit in ambient intensity, yet the spectacle can
permanently blind your retina.
(http://www.google.com/search?q=Bailey%27s+Beads)

Your high-brightness LEDs are not as bright as the photosphere, but a
similar effect is operating.


.