Dan's mugshotDaniel H. Bennett was born in London in 1965 and lived in England until moving to the United States in 2000, settling in Northern Colorado.

His interest in vision and observation of the behavior of light has been life-long. On a trip to France as a young man his hosts called him “Monsieur Tête-en-l’air” (Mr. Head-in-the-air) due to his always watching for halos, rainbows, sun-dogs (parhelia), etc. He was particularly influenced by a book written in 1939 (published in English in 1954, Dover) by Professor M. Minnaert, called The Nature of Light and Colour in the Open Air. A Field Guide to Time-Varying Light Sources was conceived as a modern successor to that book, and adopts a similar approach, while revealing the secrets of modern light sources.

Daniel is married with four children, a motorcycle and two accordions.

Buy the book!

The Field Guide is available from Amazon and other outlets.

The book's front cover

ISBN-13: 978-069-236090-3

ISBN-10: 0-692-36090-5

LCCN: 2015900348

Purchase the book on Amazon!

The Blog

Here's my blog, where I'll write articles of interest, things I've learned, tutorials, suggestions for lights to go look at, musings, etc.

Saturday, 07 February 2015 15:23

Welding and laser cutting at Walker Mowers

Written by

A mower from WalkerI had the chance to take a tour of Walker Manufacturing (home of the high-end commercial mowers) this week. This was my first chance to see electric welding equipment in action, so I took the opportunity to eyeball-jiggle at the bright welding spot. Sure enough, it's time-varying, but it turns out it's varying in two ways:

  1. It fluctuates in brightness a lot, as you would expect when welding is taking place.
  2. But it also flashes on and off rapidly, probably at 60Hz or 120Hz, which shows that its power is modulated by the A/C cycle.

Obviously, one shouldn't do this for too long; but actually, eyeball jiggling has the effect of reducing the amount of energy reaching any one spot on your retina. As long as you don't stare at it like a deer in the headlights, you'll be fine.

I also had the chance to see a heavy-duty laser cutter in action. It's cool! It takes large sheets of steel, which can be up to half an inch thick and weighing up to 2000 lbs, and it cuts shapes out of them as if they were butter! I was able to observe the bright spot right where the cutter is melting the steel, and sure enough, there was a regular variation in brightness. It seemed quite fast, maybe 200 or 300Hz, though it would need a photograph to allow one to measure the frequency. I'm pretty sure I wasn't seeing the laser itself, but variations in the temperature of the melting spot, maybe. The variations were fairly subtle.

It's always worth jigglin' at stuff - you never know what you might see!

Last modified on Saturday, 07 February 2015 15:48

Site design

This site is powered by Joomla! CMS. The template is "Cast" from Joomlage, modified here and there. The gallery is powered by RokGallery. All design by Dan Bennett.


All content on this website, including images, videos, text and material from "A Field Guide To Time-Varying Light Sources" is © 2023 Daniel H. Bennett / / A Bear Peering Round A Rock, and may not be reproduced without permission. All rights reserved to the extent of applicable law. Exceptions: third-party images, which are credited as applicable, third-party embedded videos and public domain images.