Dan's Data letters #205
Publication date: 16-Dec-2008.Last modified 03-Dec-2011.
Not great for pictures of hummingbirds
Your photo of "The Three Sisters at 2:37 in the morning", during a full moon... is it really?
It looks like a day shot, but I don't know much about photography.
Bianca
Answer:
Yes, I really took that picture in the middle of the night. It's a 30-second
exposure, though.
Moonlight is just sunlight that's bounced off the moon, so it's regular full-spectrum light; there just isn't very much of it. The very brightest full-moon night that can possibly happen lights up the landscape with an intensity of about one "lux"; direct sunlight is about 100,000 lux.
The colour-response "cone" cells in the human eye don't work at low illumination levels, leaving just the black-and-white "rod" cells. That's why everything looks black-and-white - and kind of grainy, because not all of your retinal cells are contributing to the image - when there's very little light. The threshold for colour vision is actually about one lux, which is why most people can see a little colour by the light of a full moon.
But even below one lux, the colour is all still there. It's just too dim for a human to see. All you need to make the colour visible is something that has better light sensitivity than the human eye.
The sensors in digital cameras and the film in analogue cameras aren't as sensitive to light as the human eye, but they have the advantage that you can just leave the shutter open and expose one picture with many seconds, or minutes, or even hours, of light. If you let the light all pile up for a while, bang, there's your colour. That's what I did with the two-in-the-morning picture; it's a thirty-second exposure by moonlight.
You can't do this if your subject or your camera move during the exposure; you'll just get a big blur. But if you've got a camera on a tripod and a subject that just sits there - a building, a tree, a statue - then it's easy.
(You can see the effect of the long exposure in the trees in the bottom-left corner of my moonlight picture. The trees look all fuzzy because they swayed in the wind during the exposure.)
Compact digital cameras aren't much good for long exposures, because their sensors are very "noisy"; the tiny photosites on the sensor fire randomly all the time, and the longer you leave the shutter open for, the worse the noise gets. They can usually manage a few seconds without turning the picture into a complete noise storm, but that's it. The mad race to put the biggest possible number on the "megapixels" sticker means that compact cameras are, if anything, getting worse in this respect as the years go by.
Bigger digital cameras (usually digital single lens reflex cameras, or "DSLRs") have bigger sensors that are much less noisy. Even an entry-level DSLR will let you take multi-minute exposures these days. And film has no long-exposure noise problem at all; if you've got an old-style all-mechanical film camera with no batteries to go flat, you can leave the shutter open all week if you like, if you'd like to get a picture of some place that's almost - but not quite - totally dark.
(If there's genuinely no light at all, it doesn't matter how long you leave the shutter open for, because even a trillion times zero is still zero. If the bottom of your coal-mine has some faintly luminous lichen on the wall, though, you may get a picture after all!)
Here, for instance, is someone's 24-hour exposure of "a very dark cellar", taken with a pinhole camera that needs long exposures at the best of times.
People use very long exposures, or multiple "stacked" short exposures, for astrophotography. There's a lot of colour in the night sky, but - once again - it's too dim for humans to see. If you look through a big telescope at a nebula that looks brightly coloured in your astronomy textbook, for instance, you're only going to see it in black and white. Point a camera into the telescope eyepiece and take a long exposure, though (after setting up a doodad to make the telescope track the moving night sky so the image stays in one place...), and the colour will become visible.
First, purée 3,000 fireflies
The other day, I heard about this company, Vu1, getting a large donation to continue their product development. They have nothing on the market yet, but they claim to be making a lightbulb shaped exactly like an incandescent bulb with the power draw and lifespan of a compact fluorescent with no mercury usage and any conceivable mix of visible light, apparently, if one reads the FAQ. In their press releases, they imply it uses similar technologies to a CRT monitor, shooting electrons at a phosphor screen. They then promise it's fully dimmable, and will cost about the same price as a nicer CFL.
Is this a legit company with legit science on their side? The fact that I've never heard of them and don't see any product demonstrations makes me skeptical, but at the same time their claims are not completely outlandish. The usual scam site tends to pitch the future technology as being able to do anything and everything, but here they claim to be making a very specific kind of bulb to start with, rather than every kind of bulb at the hardware store.
I'd probably be better able to cast judgement on my own if I knew how efficient getting light from a CRT monitor is, and more about that technology in general. The dimmer claim makes me wonder, as I expect there would be some sophisticated circuitry to make it work, as with a CFL light.
They plan on having their first product out mid-2009. Think LED lighting will destroy them shortly after?
Tim
Answer:
I don't know. As you say, Vu1 don't seem to be making any technically outrageous claims.
Their "electron-stimulated luminescence" technology isn't meant to be any more efficient,
and definitely not any cheaper, than compact fluorescent.
(Their claim of "perfect light quality" sounds a bit dodgy, though, since they're exciting a phosphor to create light. There's no such thing as a "white phosphor"; you have to mix other colours to get output that looks like white, and I see no reason to suppose it's any harder to make a fluorescent lamp with good colour rendering than it is to make a Vu1 lamp with the same phosphor mix.)
I question whether there's actually a need for a "less polluting" CFL, given that there's only a tiny amount of mercury in a CFL and it just wafts away on the breeze if you break the bulb. But competition is good, and these new lights may indeed be neat for coloured lighting and dimmability, never mind the pollution aspects. Just reducing the amount of glass that goes into the lamp is a good thing - apparently the Vu1 lamps use similar glass parts to an incandescent bulb, instead of the fiddly whorls and spirals that go into a CFL.
Note that if they really are making light in the CRT way, by slamming an electron beam (or "spray", I suppose) into phosphor on the inside of glass, then they may have X-ray emission problems to deal with. CRTs deal with this by using leaded glass, which is not actually a really serious pollution problem (the lead stays in the glass, and doesn't leach out into groundwater at the dump), but which would still make the "cleaner, greener" claims a bit silly.
CRTs are quite miserably inefficient, in light-per-watt terms. But they're not trying to make as much light as possible; they're trying to display a high-resolution, balanced image. I can believe that it's possible to get fluorescent-level efficiency out of some variant of CRT technology.
White-LED efficiency is increasing rapidly - just in the last few years, white LEDs have gone from incandescent-bulb to fluorescent-lamp lumens per watt - but LED light bulbs are still much too expensive per watt of light output to be practical for general applications. It's possible that they'll be supermarket items in another few years, but I'm not holding my breath.
We shouldn't have long to wait to see if the Vu1 lamps are any good, anyway. As you say, Vu1 say they'll be selling bulbs in 2009.
See also: Precious Bodily Fluids
My son mentioned at dinner last night that microwave ovens transform food into substances that the body regards as toxins, hence destroying the nutritional value of everything placed within. He couldn't cite sources other than "the Internet", but I refrained from rolling my eyes until I could get to a computer.
No surprise, just about everything that comes up in a cursory search refers to a handful of dubious studies, with these pages being pre-eminent:
http://www.mercola.com/article/microwave/hazards.htm http://www.mercola.com/article/microwave/hazards2.htm
He had also mentioned a plant experiment, but I quickly found a Snopes page debunking that one.
Oddly, the only refutations I could find that addressed the "studies" were from your neck of the woods.
I'd like to thank you lot for carrying the Torch of Quashing.
John
Answer:
Yeah, Joseph Mercola is, so
far as I can see, a world-class bullshit artist. "Energy
medicine",
acupuncture, vitalism, actual
literal guardian angels... and of course he makes a lot of money by selling "dietary
supplements", which regular doctors will tell you most people do not need, if they eat
a decent diet of normal food. But ah, if the nutritional content of normal food has
been destroyed by one or another of the terrible things that supplement-sellers keep
talking about, then...
There haven't been many studies of the damage done to food nutrients by microwave ovens (beyond that done by any equivalent amount of non-microwave heating; it's uncontroversial that if you boil your veggies to death they won't be as good for you), because nobody has come up with a theory, or even empirical evidence from an uncontrolled investigation, to suggest that any such damage actually occurs. So far as I know, the only possibly harmful chemical changes to food that can be created by microwaving are the exact same ones that'll happen if you (over)cook it normally.
There are theories about weird molecular resonance effects, popular among people who think mobile phones or wireless networks are harming people, as well as among people who think microwaved broccoli is dangerous. There are also a smattering of actual studies that suggest something beyond heating may be going on - there was a Stanford study in 1992, for instance, which found that microwaved frozen breast milk had lower levels of anti-infection components than conventionally thawed milk.
This was a quite remarkable result, but (a) doesn't say anything about food nutrients, and (b) has not to my knowledge ever been replicated, which is a problem. You can find one study to support just about any crazy idea; there's no reason to get all upset about the results unless someone else has managed to duplicate them.
More interestingly, there's "microwave chemistry", in which chemical reactions are accelerated by microwave irradiation much more than pioneers in the field expected, from simple heating effects.
We've done more study of that, now, and (a) some stuff that seemed spooky has turned out not to be, and (b) some genuinely odd stuff - like liquid mixtures of substances with different microwave susceptibility being unevenly heated, down to the molecular level - is not, as far as I can see, relevant to food heating, unless you're heating some pretty weird food.
Dollar Auction dot com
You've probably had people email you about this before, but I think your special touch is used in writing about the scam that is swoopo.com. Seriously - this site makes the Firepower dweebs look like saints!
Dean
Answer:
Is it a scam, though? I don't think it is.
I mean, it's not a good deal to have to pay a buck every time you increase the bid price of an item by 15 cents, but Swoopo seem to disclose this quite clearly.
And right there on the front page, they've got auctions ticking up, with the price flashing every time someone spends another buck to increment it. You can see, right there, that many products aren't actually very likely to go for a very low price, and they don't hide this - when something finally sells, they leave it sitting there so you can see what it went for, until you refresh the page. Just watching the auctions in progress makes perfectly clear that only one of the people involved in incrementing each price is going to get anything back, and that an awful lot of increments go into most of the items.
As I sit here typing this e-mail, I've seen a copy of Mario Kart with the Wii wheel add-on go for $39.30. The retail price is $45 or something, so nobody got much of a deal there; the winner probably paid more than retail, when you take the dollar bids into account.
But I also saw a Logitech QuickCam Pro 9000, street price at least $60 and possibly more than $80, go for $7.65.
(Swoopo list its price as "Worth up to $99.99", which is a bit cheeky, but actually is the MSRP for the camera. It's like the gameshow "The Price Is Right", which I always refer to as "The Price Is Highly Inflated".)
I wouldn't be surprised if quite a few of these less "sexy" items go for excellent prices on Swoopo. I presume they've factored that into their business model, and make back the money on high-dollar items like DSLRs and big TVs, which can be expected to attract thousands, if not tens of thousands, of one-dollar bidding fees.
I think Swoopo would only qualify as an actual scam if, for instance, they didn't send people goods that they'd bought, or if they had shill bidders on their payroll, pumping up prices and/or "winning" auctions and then not claiming the goods. Or if they created whole phantom auctions, so they could have some impressive super-low prices to scroll along the top of their front page.
If they chose to do these things then they could probably get away with it quite easily, but I'm not aware of any evidence that they do. I bet they're doing perfectly well without having to cheat. (They're not soaking buyers on shipping, either; they only deliver within the USA, but the postage for that Logitech webcam was only $US9.80, which is OK. Postage for the Mario Kart package was $US4.80.)
So Swoopo might actually be a good place to buy low-dollar items like webcams, especially if you do actually enjoy this novel cross between gambling and shopping.
It's like lottery tickets. They're always a lousy bet, and there are some people who treat them like an investment scheme and sink large portions of their income into them. There are some very dumb people in the world - look at the ones calling a "lottery addiction hotline" because they think the people there can tell them what numbers to play, for instance.
And those people certainly are 100% welcome at Swoopo, in casinos, and at the racetrack. Even a person with something resembling financial sense who chose to buy stuff on Swoopo all the time would, I think, very probably end up wasting an awful lot of money.
But if you just buy a single lottery ticket once a week, because you enjoy the frisson of excitement that comes from maybe having a million dollars right there in your pocket, there's no harm done.
If you enjoy Swoopo in a similar way, I don't see any harm in it.
(The other day, Jeff Atwood wrote a piece on Swoopo. He notes that they're a drop-shipping outfit, so they have to be absolutely raking in the cash. He also says that he thinks it might be illegal, though, and I'm not sure that there's any reason to say that. Well, unless the Swoopo business plan happened to be prohibited by some state's gambling statutes or something, like harmless primary-school raffles that get busted by the local Gaming Commission.)
