Saturday, 27 November 2010

Beware of natural food

While recently rereading Reay Tannahill's awesomely informative Food in history, I came across the following paragraphs in Chapter 21, which I thought rather striking although not really surprising.

In view ... of the extravagant publicity given to artificial additives, this is perhaps the place for a reminder that quite a number of natural, healthy, real foods would not be on the market today if they were subjected to the kind of tests that have to be undergone by the additives of commerce.

Caffeine, the natural stimulant in coffee, is fatal to humans at a dose of about one-third of an ounce. Nutmeg is hallucinogenic. Two pounds of onions a day are enough to cause anaemia. Rhubarb and spinach contain oxalic acid, which builds kidney stones. Carotene, which puts the colour in egg yolks, sweet potatoes, mangoes and carrots, can result in jaundice. Cabbage in excess can help to cause goitre. Bran, promoted in the high-fibre diet thought to help prevent coronary and colon diseases, can in excess prevent absorption of iron and calcium. Red kidney beans, inadequately boiled, can be toxic. Watermelon seeds are claimed to damage the liver and kidneys. People have been poisoned by the solanin in green potatoes, the prussic acid in bitter almonds, the cynanide in lima beans.

Friday, 25 June 2010

Dynamic range in digital photography

In photography, dynamic range is the difference in brightness between the darkest and the brightest part of a scene. There are two problems with dynamic range: capturing it in the camera's sensor, and reproducing it on screen for people to see.

It's useful to distinguish between three levels of dynamic range.

  • Low dynamic range: the scene can easily be captured in one exposure, saved as an image with 8 bits per colour, and reproduced on a good monitor without any loss of dynamic range. A photo of such a scene doesn't need any special treatment. However, tone-mapping can still be useful to "improve the lighting".
  • Medium dynamic range: the scene can be captured in one exposure and saved in a camera raw file with 12 or 14 bits per colour; but reducing it to 8 bits per colour would clip the dynamic range. In this case you can save the raw file as several different files with different exposure corrections, and then combine them using tone-mapping or exposure fusion. These techniques compress the original dynamic range in different ways to give a result that looks pleasing.
  • High dynamic range (HDR): the scene can't be captured in one exposure without clipping the dynamic range. In this case, you can take multiple exposures with different shutter speeds, and then combine the exposures using tone-mapping, in order to compress the original dynamic range in a pleasing way.

A problem with the use of multiple exposures for HDR photography is that there are often moving objects in the scene (people, cars, leaves, waves) that cause blurring or ghosting when the exposures are combined. Photomatix tone-mapping offers some degree of automatic correction for this problem, but Photomatix exposure fusion does not; so I wouldn't use exposure fusion for true HDR photos, because there are so many things in a scene that may move. Unless you take photos inside a building with no moving objects in sight.

Yes, you can use laborious manual methods to deal with ghosting in your HDR photos. If you want to spend that much time on each photo.

Most normal scenes have either low or medium dynamic range. Anyone who often takes photos of high-dynamic-range scenes is probably going out of his way to look for them. They might be scenes with bright sunshine and deep shadow (perhaps looking into the sun), or night scenes with bright artificial lighting.

Thursday, 17 June 2010

Small white hunter

A memory fragment from my mother, early 1940s:

Hate to remember it now but on holidays in Wiltshire (aged around 9 to 11) I used to go out with my aunt Rhoda's husband Ted and shoot rabbits. Meat rations were stingy and my grandmother (she and Rhoda were staying in Wiltshire for the war) welcomed succulent rabbit to stew and feed us all.

She adds later:

... it's a good job my rabbit-shooting days were so long ago because, never mind it being illegal now, it was illegal then. We were trespassing on someone's land for starters and at my age I should never have been allowed to handle a gun, let alone use it. I don't know whether one needed a licence for a gun then but I'd bet my bottom dollar that Ted didn't have one.

I understand from Wikipedia that a gun licence has been required in the UK since 1870; originally anyone could have a licence who paid for one, but from 1920 it became necessary to get approval from the police.

Friday, 7 May 2010

A libertarian view of the British political parties

I'll keep this brief.

  • The Labour Party is fundamentally opposed to liberty.
  • The Conservative Party doesn't believe in liberty, or anything else.
  • The Liberal Democrats should believe in liberty, but their policies fail to confirm this. A confused party.
  • The Libertarian Party is the only one worth supporting, but it's very young and very small.

The least bad result of the election currently in progress might be a Con-LibDem coalition. Ideally, they might veto each other's sillier ideas. Though things seldom work out ideally in politics.

Saturday, 17 April 2010


Cliology may be defined as the science that seeks to understand and predict the course of history—from Clio, the Greek muse of history. As far as I know, no such science is currently practised, but it was named and interestingly discussed in Michael Flynn's novel In the country of the blind (1990).

Such a science was already imagined in the 1940s by Isaac Asimov under the name of psychohistory, but I have a feeling that Flynn's name may triumph in the long run, because by now we already have the genuine scientific fields of cliometrics and cliodynamics, both of which could perhaps be seen as early precursors of cliology.

It is, of course, impossible to predict the course of history with accuracy, but statistical analysis and a general understanding of historical forces may eventually enable people to predict history well enough to be of some use: just as a weather forecast may be of some use even if it's sometimes wrong.

In the fiction of both Asimov and Flynn, cliology is more or less a secret science, used to predict the history of a population that's unaware of cliology. Asimov, at least, felt that the predictive ability of the science would be spoiled if the whole population under study was aware of cliology and of its specific predictions.

This awareness would make prediction more difficult, but I think not necessarily impossible, for two reasons.

  • People have always attempted to predict future history, and there are some future historical developments that can be predicted fairly well without advanced science. Sometimes, people aware of such predictions can change their behaviour to avoid the predicted event; sometimes, even knowing the prediction, they can't avoid it. I don't think this will change in any fundamental way if the predictions become more accurate.
  • Predicting the future of people who are aware of the prediction is a kind of recursive problem, and I think science in general is not helpless in the face of recursive problems. Computer programs, for instance, routinely include recursive functions.

Even if recursive prediction doesn't work, a non-recursive prediction would be far from useless. It could be seen more as a warning: if you carry on the way you're going, this is what will happen.

Monday, 25 January 2010

Al Stewart rides again

Although I have a good collection of Al Stewart albums already, in November I acquired two more, A piece of yesterday (double-CD compilation, 2006) and Sparks of ancient light (new material, 2008).

I'm pleased with both. I had most of the songs on the compilation already, but it's the best result of remastering I've heard so far: the improvement in sound quality is really worthwhile, even through iTunes and mid-fi loudspeakers.

I now discover belatedly that there's a five-CD compilation called Just yesterday that maybe I should have chosen, had I known about it.

Sparks of ancient light is a minor album that won't convert anyone into an Al Stewart fan, but if you like him already this is superior to some of his other later albums (Down in the cellar is also worth trying). It's a pleasant and lively album on which he sounds younger than 62. As usual, the songs mostly have historical themes; there's even one about Hanno the Navigator.

Sunday, 17 January 2010

Death of a dupe

Akmal Shaikh was executed in China in December after being caught entering the country with 4 kg of heroin in 2007. It seems that he was tricked into carrying the heroin and may not even have known it was in his luggage.

Drug smuggling (even if intentional) isn't a violent crime and I don't support the death penalty for it. But the interesting thing to me about this case is that most of the outcry about it from other countries (the UK in particular) was that Shaikh should have been let off on grounds of mental illness.

Eh? Surely the rationale for executing someone is that he's a danger to other people, and you can permanently nullify the danger by executing him.

Does mental illness make a dangerous person less dangerous? I don't think so. Why, then, is it relevant? Surely, any court considering execution should be trying to determine how dangerous is the accused, not how sane he is.

In this case, Shaikh seems to have been stupid, but probably not sufficiently dangerous to be worth executing. (I've read that he had a previous conviction for sexual harassment, so he wasn't harmless.)