Bio
Daniel 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.
ISBN-13: 978-069-236090-3
ISBN-10: 0-692-36090-5
LCCN: 2015900348
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.
I'm excited to be the exhibiting artist this month at the Land Of A Thousand Hills coffee shop in Roswell, GA!
These photos are all from my time-varying lights project, and were selected from my online gallery: http://photo.peeringbear.com/p188493375 (where you can order prints if you don't happen to be in Roswell, GA... 
)
Two nights ago I took a photo of the star Arcturus, using my Canon 70D camera with a 200mm zoom. The exposure time was 1.0 second, during which time I hand-held the camera and moved it during the shot. Here's the result.
The trace shows a massive number of variations (over 800!) of brightness and color. This is scintillation, better known as twinkling. Our eyes aren't able to see all these variations because (a) they're too dim, so we don't see the colors, and (b) they're too fast, so we see only the largest and slowest variations in brightness as twinkles.
The cause of these variations is atmospheric - the star itself is NOT twinkling! If you took a photo like this from the International Space Station, it would be a constantly bright, slightly orange line with no variations in color or brightness.
This type of photography is really easy... go try it!
Featured on Light Painting Photography website
Written by Dan BennettI'm very excited to be the current featured artist over at Light Painting Photography, Jason Page's great nexus for all things light painting. Jason worked with me to create a great interview, sprinkled with many of my photos and links back to here. Thanks, Jason! It's humbling to see my rather unique photography being showcased to such a creative crowd of people, and I hope that it stimulates some new ideas and techniques. I'm looking forward to seeing where this new endeavor takes me.
In case you weren't already convinced that most street lights are time-varying, here's proof. This is a shot I took of a small US city (I don't know which) from an airplane at night. I swept the camera while taking the shot, using a 1/10 second exposure time. As you can see, there are many lights and groups of lights which show strong periodic traces. Most of these lights are pressurized sodium street lights, which flash at 120 times per second (in the US).
I had to adjust the exposure and tone curve in Lightroom to compensate for the fact that a city at night isn't very bright as far as a camera's concerned; and when you sweep the camera, it's even dimmer.
Christmas is coming... and LED Christmas lights are appearing. Almost without exception, these LEDs flash at 60 Hz (in the US, 50 Hz in Europe). The result: move the camera and you'll see the dashed-line trace of each LED. Here's an example...
Inspired by something I saw online, I decided to try reflecting an image in horizontal and vertical axes using Photoshop. Here's the result:
The original, non reflected image can be seen here.
Cellphone camera for checking out light sources
Written by Dan BennettI've made a cool discovery: cellphone cameras (and probably most cameras with a live display (sometimes called "live view") can be used to observe time-varying light sources.
Simply open the camera app and point the camera at the light source of interest, then rock the camera rapidly up and down so that the light source paints a trail on the screen. In most cases, you'll be able to see the trail breaking up into dashes or repeated images, showing that the light source is time-varying. It's not as good as eyeball- or mirror-jiggling (see my "How To See" page), but as a quick way to see if a light has time-varying behavior, it can be useful.
I've tested it so far on three cellphones: LG G4, Apple iPhone 6+ and Motorola Droid Mini. It helps to let the camera focus on the light source first before rocking the camera up and down.
LG's G4 cellphone is (almost) perfect for TVL photography
Written by Dan BennettI've just moved to the LG G4 phone, and was excited about its camera's manual mode. Tonight I had a chance to try it out. I photographed this restaurant, which has a line of white LEDs around its windows:
By using the camera's manual settings, I captured this image:
The time-varying behavior of these LEDs is very easy to see with the naked eye, and may well be one of the easiest subjects for vision jiggling.
To get this image, I selected the following settings:
- Manual focus (so that it would not be trying to focus while taking the shot)
- ISO 500 (to underexpose the image so that I get the lights, not the whole scene)
- 1/8 second (to capture for long enough to give me plenty of dashes in the traces)
The primary weakness with the G4's camera is that there's an appreciable delay between pressing the button and the shot being taken, and since you have to keep the camera moving it's unpredictable what you'll capture. The solution is to take several shots until you get what you want. Aside from that, though, and the lack of optical zoom (which isn't too much of a problem for this type of photography), the G4 makes a great pocket tool for the photographer of time-varying light sources. Highly recommended.
I'm ramping up on Twitter. Feel free to follow me: @TimeVaryLights . Enjoy!
This is a slightly cropped region of a photograph I took at Indianapolis airport in March 2015. It shows a long building with pressurized sodium lights along the front. The cool thing to note are the regions where the traces show strong diagonal patterns to the light and dark dashes. This is due to the fact that the electrical contractor who wired up the lights was fairly rigorous in following a 1 - 2 - 3 - 1 - 2 - 3 sequence when selecting which phase of the three-phase electrical supply each light should be connected to. This is a sensible approach as it balances the load nicely. And, for those who know how to see it, it makes a cool pattern!
I've decided to drop one of the distribution channels that my book could - maybe - be sold through. That has allowed me to drop the list price from $32.99 to $25.99. This price change takes effect immediately on Createspace's page, but may take a day or two to be reflected on Amazon's page.
Exciting news regarding my book: Today, it's being featured on the Atmospheric Optics Picture Of The Day website! Although most of the book isn't concerned with atmospheric optics per se, the section on twinkling stars certainly qualifies; and the website's charter is pretty broad, so it fits right in.
The permanent link to the page is http://www.atoptics.co.uk/fz1109.htm
I asked the guy who runs the site (in which I had a photo published a while ago) if he would feature the book, and he's done an excellent job! He obviously had a lot of fun building that collage.
His audience is my audience, so I'm hoping this will help to get the book some targeted publicity.
Enjoy!
I 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:
- It fluctuates in brightness a lot, as you would expect when welding is taking place.
- 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!
20 copies of the book arrived today - the first time I've seen the final product in physical form. This is a wonderful moment for me... the tangible fruit of a lot of labor!
More...
It seems ironic (and a little deflating, frankly) that now that the hard work's done, the hard work starts! Writing the book was a labor of love, and it had a very clear end-point in view: finish the book and get it published. That goal has now been fulfilled, which is great! However, the biggest down-side of self-publishing is that the marketing of the book lies squarely on my own shoulders. Of course, there are ways to do this, and I've already set some wheels in motion, which should hopefully bear fruit down the road. But it would be wonderful if something happened to make it "go viral" - always the marketer's dream.
The biggest challenge with this book is not that it's not interesting or captivating - everyone who's seen it says it's both - but that it address a completely new topic, one that nobody even knows exists. How can people be expected do a web search on a topic that they don't even know they'd be interested in?
The key to marketing, of course, is to get the book in front of audiences that are highly likely to be interested in observing time-varying light sources, once they're made aware of the field and its possibilities. To do that, I'm starting to reach out to key people who have websites and/or YouTube channels that a lot of people follow, but which are in closely-related fields, such as observing/enjoying atmospheric optics, or photography. These key people are known as "influencers", and are the lynch-pins to reaching audiences. I'm definitely hoping they'll be able to put some wind under the wings of my book.
Here's to successful marketing!
Comments welcome. :)
Well, now that the print edition is out there, I'm about to start work on the eBook for Kindle. It's going to take some work, because, unlike a novel, this book has over 300 pictures and captions! Laying all of that out in a reflowable format so that it works on any size of device without the captions and pictures getting horribly separated from each other will be a challenge! Thankfully, Adobe InDesign (which is what I've laid this book out in) does a pretty good job of exporting to the epub format, which is one of the formats that Amazon can accept for a Kindle publication. It's going to take a little while to make sure the output is exactly what I want, but I'll get there.
And... the book has already appeared on Amazon in the US and in the UK! Amazing - the CreateSpace process says it'lll take 3-5 days. Maybe that's for the non-English European sites. For example, le livre ne se trouve pas au site français. Oh, sorry... The book isn't on the French site yet. :)
Today my book went live on CreateSpace.com! After four years of working on it (not all the time, of course), and a major push over the last three months or so, it's finally a Real Book! With Pages, and a Cover and Everything!
I am sooo excited!
The book is published through CreateSpace, which is a division of Amazon which allows people to self-publish. The cool thing is that the book is printed on demand - i.e. when someone orders a copy, a copy gets printed, bound and shipped. This is wonderful, because there's no need for me to fund a print run, no up-front inventory, or anything!
In a few days' time, it'll appear on Amazon's websites in the US, Canada and Europe.
This book is totally a labor of love - observing time-varying lights has been an interest for me all my life. So it's a wonderful milestone in my life to see it in print. I am one happy guy. :)