Led Lenser Torches for night birding

To: "Peter Shute" <>, <>
Subject: Led Lenser Torches for night birding
From: "Robert Inglis" <>
Date: Sun, 20 May 2012 17:20:56 +1000
One of the unfortunate aspects of the marketing blurb for these LED torches is the use of "lumens" as a light output rating. It is very difficult to compare a 'lumen' rating with a 'candlepower' rating which has been the usual way hand held spotlights have been rated in the past. As I understand it, lumens is best use as a rating for an unfocussed light output and candlepower is better suited for a rating of a focussed light output. As far as what we're accustomed to in light outputs from spot lights, consider that many commonly available halogen filament spotlights are rated at over one million candlepower. No matter how you convert an output rating in lumens to an output rating in candlepower I would suggest that a spotlight with an output of a million candlepower would, more than likely, be brighter than that of a LED torch with an output of 1000 lumens. The main advantages of LED spotlights over halogen filament spotlights are in the size of the LED spotlight and the operational time between recharging of the batteries. There is definitely no price advantage in LED spotlights if the same light output is required.

Also, many car headlights have higher lumen outputs than many of the higher powered LED spotlight torches. Some of those headlights are very annoying (especially to people developing cataracts) but they don't seem to be causing a lot of permanent damage to people's vision.

Bob Inglis
Sandstone Point

-----Original Message----- From: Peter Shute
Sent: Sunday, May 20, 2012 4:03 PM
To:  ; 
Subject: Led Lenser Torches for night birding

I'm sure the inverse square law applies, but I wonder if these highly directional beams are still dangerous at greater distances than we're accustomed to. Taking directionality to an extreme, lasers are dangerous, or at least very annoying, from a great distance.

Let's assume we're still talking about human eyes.

Peter Shute

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