Just got back from Thailand, and I am still battling jet lag. The trip and wedding were awesome. One of the highlights was the Flight of the Gibbons–a high wire zip line through over three kilometres of rain forest. The park is part of a larger conservation effort dedicated to saving Gibbon monkeys. If you go to Thailand make sure you check out the Gibbons.
With apologies to William Blake Photon! Photon! Forming Flight, In the lab as dark as night. What nonlinear order Chi Could spring entangled Symmetry?
In what distant laser dyes Sparked thy subtle wave-like guise? What on resonance transpires? On what level lasing fires?
And what calcite, and what part? Could squeeze thy spin with such art? And when thy mode began to lock, What short pulse, and what short clock
What the Amplitude? What the Phase? Of this single-photon craze? What the particle? What dread thought In what paradox are we caught?
When the stars threw down their spears, That travelled for a million years, Did the correlations bunch? Just like Twiss and the other's hunch?
Photon! Photon! Forming Flight, In the lab as dark as night. What nonlinear order Chi Could spring entangled Symmetry?
—Krister Shalm 2010
This is the poem that I wrote for my PhD thesis. I have been meaning to post it for awhile now.
Jaime, Martha and Heather are big Body Rock fans. Last week they go together to burpee Toronto as part of the Burpee Everywhere challenge. They travelled the city executing burpees at various landmarks and videoing themselves, and then asked me to cut the footage together.
Jaime has been trying to get me to start working out with her and I might give it a shot this fall—lord knows I need to get back into shape. There is a mini fitness craze at the IQC right now with people joining Fitocracy, an online real life exercise RPG where you get to "level up" by doing exercise. I am not sure I want to join yet, but I know it has motivated many people around me to start working out regularly.
Physicists can have fun too! One of the groups I work with at the Institute for Quantum Computing took a field trip to the Erbsville Kartway here in Waterloo. We had lots of fun go karting and playing mini golf. Congrats to Evan who destroyed everyone else at mini golf.
For those of you who missed it in person, the video for the Quantum Physics & Harry Potter is now live. Dan and I had a lot of fun putting this on and are hoping to repeat the show sometime in the winter. A big thanks to Peter Kovacs for shooting and editing the video.
Jaime and a group of her friends get together once a week for a girls night. This week they used old magazines to make a collage called a dream board. I set up a camera and captured a time lapse of the event. I am beginning to like this time-lapse business.
Here is a video recap of Lindystock 2011 that I put together. At the end of July Toronto Lindy Hop put on Lindystock, a dance camp near Algonquin park about 4 hours north of Toronto. This is not a camp where you go to learn to dance, but, rather, a camp for Lindy Hoppers to hang out, relax, and bond. I had the pleasure of being involved in the organization of the previous two Lindystocks, but this time it was nice being able to take everything in without having to do any organizing. The weekend was amazing! The venue the organizers found this year was superb and much better suited to the event. There was hiking, canoeing, swimming, volleyball, frisbee, soccer, and of course dancing. I made lots of new friends and reconnected with some old ones. Next year I am definitely signing up again.
This past weekend I shot my first time-lapse video of a street festival, called Square 2 Square, that has been running this summer in Waterloo. Every few Sundays the main street through town is designated a car free zone. Local business set up booths and fun activities take place. During the last Square 2 Square festival I took some footage of a street water fight near my house. This time around a good friend of mine, David Trinh of Hep Cat Hoppers fame, set up a Lindy Hop booth. I set my camera on top of his car and set my camera to take a picture every 3 seconds. Nearly three hours and 3000 pictures later this is what happened.
Another reason I love Waterloo: during the three hours I was out on the street I ran into seven other physicists.
Alex Cherney is an Australian photographer who has taken some incredible images of the night sky. His photos have won numerous awards and are routinely featured on NASA's astronomy photo of the day site. Below are two of my favourite videos from Alex. They remind me of the superb time lapse video taken at the Very Large Telescope Array. [vimeo]http://vimeo.com/15583376[/vimeo] I love the reflections in the lake and the music from the didgeridoo in the video. The next video was shot of one-and-a-half years and won first place in the STARMUS astrophotography competition. For more incredible footage check out his Vimeo page.
I just got my intervalmometer (a remote control that can be programmed to take photos at regular intervals) and am excited to try out some time-lapse photography. When it comes to photography, I am always amazed and inspired by people like Alex.
You can purchase some of his prints on Redbubble. I am buying a copy of this astounding panorama to hang in my living room.
I recently bought a Light Craft Workshop Fader ND Mark II variable ND filter to use for shooting videos, and was curious about how well it performs. I used the Fader ND to film the water fight that broke out near my house last week, and was pleased with the results (Vimeo version embedded after the jump). But to be more thorough I decided to conduct a series of tests of the Fader ND. In short, the optical quality of the filter is very good with little degradation of the image. The filter is also neutral throughout its useable range of attenuation introducing almost no colour shift. I strongly recommend it to those looking for a budget variable ND filter. Read on for my full review of the Fader ND Mark II.
[Update] I have added some resolution tests of the Fader ND at longer focal lengths at the end of the post.
Introduction
Shooting video in daylight is challenging; it is often so bright out that a high shutter speed on the camera is required. This can lead to jerky and unnatural motion in moving subject, and force the use of high apertures. A solution is to use a neutral density (ND) filter in front of the lens. An ND filter blocks out some of the incoming light allowing a slower shutter speed to be used. Good ND filters attenuate every colour equally (hence the term neutral) while bad ND filters can introduce an unwanted colour cast.
The two main solutions are to use stack of fixed ND filters to control the light level or to use a single variable ND filter whose strength can be adjusted. For my purposes, I decided to go with a variable ND filter. Most variable ND filters are made up of two polarizers that can be rotated with respect to one another. Light travels through space as a wave, and its electric field oscillates back and forth similarly to how a water waves undulates up and down. While water waves can only move up and down, light can oscillated in all directions (for example, side to side, up and down, diagonally, and even in a helical spiral). The direction that light oscillates is known as its polarization.
A single polarizers will cut out 50% (1 stop) of the light from an unpolarized light source like a light bulb. After passing through the polarizer, the light has a definite polarization. If a second polarizer, aligned with the first, is inserted next then all of the polarized light will pass through. If instead the second polarizer is rotated by 90 degrees all of the polarized light is blocked. By rotating the second polarizer in between 0 degrees and 90 degrees the amount of light passing through can be controlled.
The problem with using polarizers to create a variable ND filter is that the polarizers are not always of a high quality. There can be a serious loss of resolution if the optical quality of the polarizer is not good. Poorly manufactured polarizers, with extra materials between them, can also lead to a variable colour cast being introduced into the image–as the polarizers are rotated the colour cast changes.
There are several options on the market for variable ND filters. The deluxe higher end models are the Singh-Ray variable ND filters that can cost several hundred dollars. There is also a newer product out by a company called Light Craft Workshop that makes significantly cheaper (under $100) variable ND filters. I also came across these filters on eBay sold by Rainbowimaging that are incredibly cheap (around $30). I have ordered a number of things from Rainbowimaging before, and have been pleased with the quality and service received. Because they are so cheap, I nearly bought one of these filters just to try out. I had a hard time finding any reviews on them, but did stumble upon some Youtube videos that made it look like these filters introduced a significant colour cast. It was hard to tell if this is the case, but I decided not to risk it. Perhaps one day I'll order one and do a test.
In the end, I went for the Light Craft Workshop Fader ND Mark II (second generation version of the filter). Philip Bloom, a well known blogger and film maker, has good things to say about the Fader ND, so I ordered a 52mm filter from the Canadian distributor on eBay. Again service was excellent and shipping fast. While the filter I ordered will thread onto a 52mm front element, the polarizers are 55mm. This is to help limit vignetting, but means that any other filters/lens hoods that go on in front must have a larger thread size. Every size of the Fader ND uses polarizers that are one step larger.
The Fader ND comes with a convenient carrying case as well as a lens cover (55mm in my case) that works well. The polarizers rotate smoothly and are well constructed. There are marks on the filter to help serve as a rough guide, but in practice I have not found them useful. They do not correspond to the number of stops of light blocked. This is not a fault of the Fader ND, but is a consequence of the way polarizers work. As the angle of the second polarizer changes, the amount of attenuation will not vary linearly. If the Fader ND were to introduce marks that correspond exactly to the number of stops of light blocked, the marks would be distributed in a more complicated fashion. It would be nice to have accurate markings, but for the price I can not complain.
To test the resolution and check for the presence of a colour cast, I carried out two different tests. In the first, I set up a tripod outdoors and shot a sequence of photos of a picture from the book "A New Kind of Science" by Stephen Wolfram. I do not have an Airforce test chart, but this book has very high resolution photos that contain fine patterns suitable for the test I am interested in. I am not able to calculate the resolving power of the lens with and without the Fader ND, but any major loss in resolution should be readily apparent.
Resolution Test
The resolution test was conducted on my Panasonic GH1 using the Panasonic 20 mm f1.7 pancake lens. In all the photos the aperture is fixed to f 5.0. First a picture was taken without the Fader ND to serve as a reference. The Fader ND was then screwed into place and a sequence of pictures taken with different attenuation settings. Each picture was taken with the Fader ND set to attenuate one extra stop with respect to the previous photo. The exposure was set by first halving the shutter speed and then adjusting the Fader ND until the correct exposure was reached (as I had to rely on the metering in the camera, the exposures are close, but not perfect).
When the Fader ND is set to 0 degrees there is a loss of 2 stops of light (maximum transmission). This matches Light Craft Workshop's claim of 2 stops of attenuation. Each subsequent picture represents an extra stop of attenuation. The central portion of the image is shown at 100% crop to provide an idea of the resolution with and without the Fader ND.
I am surprised at how well the Fader ND performs; there is barely any discernible degradation in the resolution of the image. The Fader ND also performs well over a large attenuation range (meaning any degradation in resolution is due solely to the quality of the polarizers and not the rotation of them). I get over 11 useable stops of attenuation which is more than Light Craft Workshop specs the filter for. Setting the polarizer close to 90 degrees (most of the light blocked) leads to appearance of a "cross" pattern that is typical for these types of filters.
To test for the presence of a colour cast, I shot a series of pictures of white sheet of paper. Without the Fader ND present I manually set the white balance of the camera. This is the white balance setting used in all shots. Next the Fader ND was screwed on and pictures of the paper taken for different settings of the Fader ND. Again, the exposure was compensated for by adjusting the shutter speed and ISO. These photos were taken in the passengers seat of a moving car, so they are blurry at lower shutter speeds. I also had some problems keeping the lighting/exposure as consistent as I would have liked, but they are still instructive. The camera settings along with the RGB values for the white in the image are shown (the images were underexposed, but that does not change the results of the test).
Again, the performance is excellent. From 2 to 10 stops there is a slight but consistent colour cast as blue suffers a higher attenuation. After 10 stops a small bluish tint appears. In both cases the colour cast is minor and can be easily corrected by white balancing the camera with the Fader ND on. What is most impressive is how neutral the Fader ND is as the attenuation is changed. Cheaper crossed polarizers are notorious for introducing dramatic bluish, greenish, and reddish colour shifts as the polarizers are rotated. This is not the case with the Fader ND Mark II.
There has been reports that the Fader Mark II performs poorly at longer focal lengths. To see if this is the case, I repeated the resolution test using my Panasonic 45-200mm zoom lens. I placed the camera on a tripod and set the aperture to F8 and the shutter speed to 1/320 of a second. First I tested the camera with out the Fader ND (ISO set to 100) taking photos at six different focal lengths. Next I screwed on the Fader ND and repeated the test. To compensate for the two stops in lost light I upped the ISO to 400. The results can be seen below.
There is a clear loss of resolution as longer focal lengths are used. There also seems to be a loss of image contrast as well. By the time 200mm is reached, the image is noticeably blurred. Shorter focal lengths are not nearly as bad. I definitely would not use the Fader ND on a longer reach zoom lens for photography purposes. For video it is probably fine where the high resolution image out of the sensor is down sampled. The significant drop in resolution is likely due to the optical quality of the polarizers used. Any roughness or tilt in the surface of the glass can lead to this decrease in quality. I have heard reports that the much more expensive Singh Ray filters as well as the Fader ND HD do not suffer this loss of resolution at longer focal lengths. Buying two high quality linear polarizers (or a linear polarizer and a reversed circular polarizer) and building your own variable filter may be another way to avoid these problems.
The Fader ND provides excellent value for the money. There is not a noticeable degradation in image quality at shorter focal lengths and the filter is neutral from 2-10 stops. My only regret is not buying a larger filter. Right now my largest lens has a front filter size of 52mm, so the Fader ND works on all of them. In the future if I buy lenses with a larger front filter I will have to purchase a larger Fader ND. If I had bought a larger Fader ND from the start I would have "future proofed" myself. Given the quality and value of the Fader ND Mark II, I will have no qualms buying a second one when the time comes. If, however, you are looking for a variable filter to use with long reach zoom lenses for photography, you are better off looking for another solution.
This week the Women in Physics Canada conference has been jointly running at the Perimeter Institute and the Institute for Quantum Computing. It has been great to see so many young and enthusiastic physicists around. Only about 20% of physicists are female[1]. Excluding the voices of so many potential physicists has impoverished our field. Left out are the many unique and varied perspectives and novel approaches to solving nature's riddles. (This problem of exclusion also extends beyond gender to the issue of wealth; Africa produces few physicists relative to its population. See this excellent Ted Talk by Neil Turok on attempts to build up a world class African physics community.)
Physics is a man's world, and for a woman to succeed she must play by a man's rules. The situation is similar in many ways to the glass ceiling women have been breaking through in corporate environments. A successful business woman I know once told me that in order to make it, she had to be a better man than her male colleagues. I think a culture shift needs to take place where women can be respected for thinking and acting like women instead of needing to conform (consciously or unconsciously) their behaviour and attitudes to be more male centric. I believe this is directly related to the lack of women role models in physics for both men and women. From my middle school days through to my PhD, the bulk of my science teachers were male. This creates an environment where the opinion and perspectives of men are more highly valued and respected than those of women. The more women that engage and participate in physics, the more these ingrained attitudes will change.
These male centric attitudes arise in different ways—some subtle and some blatant. The manner in which physicists sometimes debate and discuss problems can be brutal and cutting, a testosterone driven combativeness better suited to prize fighting. The long hours and the endless publish or perish treadmill are not conducive to having a family either. A female physicists friend told me that starting a family was nearly career suicide. Taking care of a baby, the lack of sleep, and the dramatic hormonal changes during her maternity leave made it difficult to keep up with the harsh research and publishing demands needed to secure a professorship. The bulk of established male physicists I know have families. Why should it be any different for for a woman?
While a typical physics lab is far from a stereotypical locker room, physicist could do a better job of being aware of how their actions can make others feel. Jennifer Ouellette has an excellent post on Cocktail Physics that outlines some of the challenges women face in the skeptics community. (Before reading any further, I strongly recommend you check out her original article.) Jennifer talks about the harassment and patronizing attitudes herself and others have encountered. What really shocks me is the outrageous and derogatory debate that erupted when people called out this kind of brutish behaviour in the skeptics community. I haven't seen anything nearly this acrimonious happen in physics, but I think many of the things Jennifer points out apply equally to the physics community.
Jennifer proposes a four point Manifesto for Change that I think we would do well to follow in order to shift attitudes. I have paraphrased (and adapted for a physics context) her original points below:
The more women that become physicists, the richer physics will become.
[1] This is true in other disciplines such as engineering, math, computer science, and IT. Feel free to replace the word "physics" or "physicists" with equivalent terms from these other fields. The issues women face are the same.
Leonard Susskind's brilliant introductory lectures on Quantum Mechanics from a Quantum Information stand point. If you have 90 minutes, check out the first lecture in the series. The first 8 minutes alone are well worth watching for Susskind's explanation of why modern physics appears so strange. His imagination, creativity, and force of thought are on full display in this lecture.
Leonard Susskind has made a number of important contributions to modern quantum theory and is one of the fathers of string theory.
Via Sean Carol.
Yesterday a huge water fight broke out in Uptown Waterloo near my house. The water fight was part of the Square2Square festival that shut down King street for pedestrian traffic to link the Waterloo and Kitchener city centers.
I grabbed my Panasonic GH1 and filmed the chaos; it was the perfect opportunity to try out my new Light Craft Workshop Fader ND Mark II filter on the camera. In a few weeks I plan to do a full review of the Fader ND. Edited on Final Cut Pro X.
A big thanks to everyone who turned out for the opening of the Quantum Physics and Harry Potter show last night. The show was a lot of fun. It is the first time I have seen people eating popcorn in a physics lecture! Dan and I are looking forward to the repeat performance tonight. I would also like to thank all of the IQC volunteers who helped make the show extra special, as well as Katharin, Colin, Martin, Jasmine, and Kim for all of the behind the scenes work. Here are some pictures that the IQC photographer Peter Kovacs took of the event.
It is only one day before the Quantum Physics and Harry Potter show opens! Yesterday we were at the theatre doing a tech run to make sure everything worked. I am really excited about the show! The demos are going to work really well.
As luck would have it, there is a magic shop right beneath the cinema. They have been very helpful and supportive of the show. This Thursday and Friday they will be staying open late in case anyone wants to find out more about magic after the show.
Tune in to Wednesday, July 12th episode of the CBC Radio's Ontario Morning show. I'll be a special guest explaining the Quantum Physics of Harry Potter. You can listen to the show live here.
[Update] A big thanks to everyone who tuned in. If you missed the interview, or would like to listen to it again, a recording of it is below.
Last week two different articles ran in local newspapers promoting the upcoming Quantum Physics & Harry Potter show. The first was a story by Marshall Ward for the Waterloo Chronicle. The second was a front page cover story by Greg Mercer of the Waterloo Record. Within an hour of the front page story in the record appearing, both nights of the show sold out! People say that traditional media is dying. This may be true, but they still have a tremendous amount of influence and reach.
Here is my cat trying to read the story. She makes a special guest appearance in the show to help me explain Schrodinger's cat.
The very talented Gillian Street of Urban Jungle Theatre is directing a play, i Spy, at this year's Fringe Festival in Toronto. Gillian is one of my favourite playwrights; I remember being blown away when I saw one of her pieces a couple of years ago. Definitely check out i Spy —it is sure to be one of the highlights of the Fringe this year. The show runs from July 6-17 (excluding the 11th). Here is a trailer for the show:
http://www.youtube.com/watch?v=wJ_FrRpn_b4
I was wondering how long it would take someone to turn Mitch Benn's Double-slit rap about our experiment into a Youtube video. Apparently not long at all. Here it is below. Maybe I'll take a crack at turning it into a Youtube video someday.
The Oxford English Dictionary defines an expert as > A person who has a comprehensive and authoritative knowledge of or skill in a particular area.
Experts are individuals who, through specialized training, are able to perform specific tasks that are out of the reach of others. I know what it takes to become an expert having spent most of my twenties in university earning a PhD in physics. I am an expert in a narrow field of quantum optics, and work daily with other experts in the same topic.
When experts communicate with one another they tend to use jargon. This jargon can speed the transfer of ideas, but leave those not initiated lost. When I attend talks given by experts in other fields in physics, I spend much of the time trying to decipher what the special terms they bandy about mean. The use of jargon is at best laziness; at worse it is a purposefully erected barrier designed to protect the exclusive knowledge of experts. If you cannot understand what an expert is talking about it is nearly impossible to challenge them.
Communicating effectively is hard. An idea at the cutting edge of human knowledge and experience can be complex, technical, and obscure. Unpacking an idea—peeling back the layers of assumptions and jargon—unleashes its true power. This process forces one to wrestle in new ways with an idea; to polish it until it becomes a glistening pearl of clarity that others will find precious.
I am not advocating the dumbing down of ideas. Everyday we are bombarded by sound bites and simplistic, inadequate, characterizations. One needs to look no further than the last political campaign to see this dumbing down at work. Instead of rational, earnest, discussions about the issues of the day, politicians resort to slogans and caricatures of their opponents. For an even baser example of this, just read the comments section of the typical Engadget post about an Apple product that devolves into a petulant flamewar between fanbois.
What I am suggesting is that as experts we work hard to eliminate all the barriers to our communication. When speaking with the general public try to convey the big picture of your idea. How does it fit in with their lives. Why is it important? What is interesting about it. I have found that asking these questions about my own research has dramatically improved my ability to communicate with other experts inside and outside my field (and funding agencies).
Nobody likes to be made to feel stupid; get rid of the isolating jargon and grapple instead with the essence of your ideas. Ideas want to have sex. Jargon and unneeded complexity are a venereal disease that keeps ideas from finding a mate. Good ideas get around.
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