Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!bbn!mit-eddie!bloom-beacon!hermes!jpexg
From: jpexg@hermes.ai.mit.edu (John Purbrick)
Newsgroups: sci.electronics
Subject: Re: Super LEDs from RS
Summary: What's that in w/sqcm??
Message-ID: <3258@hermes.ai.mit.edu>
Date: 2 Jan 89 17:28:36 GMT
References: <7200022@silver> <7200025@silver>
Organization: MIT AI Lab, Cambridge, MA
Lines: 11

The original article was about powerful visible LEDs, rated in candelas, which
is normal for visible light. How does this compare to infrared LEDs, which are
usually rated in terms of total watts and watts/sterradian (watts radiated 
into a unit angle at the brightest point)? Are the visible lamps catching up 
to the IR ones?

Note: Visible light, measured in candelas, is nonlinearly related to actual
power, because the candela takes into account the varying response of the eye
to different colors. An infrared lamp rates 0 candelas, although most Hewlett-
Packard IR LEDs seem to be near-infrared and emit a small amount of visible
light too. "Aids alignment", as the catalog says.