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Monday, December 20, 2021

A Trick of the Light

I've noticed this particular frame for a couple of years now, off and on, and finally got around to photographing it a week or two ago. I might have shot it before, but I can't recall.

This is a purely random welter of twigs, wet from the rain, and yet the appearance of circles, of orbits, is quite definite. I had to think about it a little to work it out.

From the perspective we're looking at these twigs, the only surfaces which reliably reflect toward our eye are those oriented to the streetlight in a particular way. The only surfaces we "see" then, are the ones that follow the orbit. The rest are lost in darkness.

There is another tree I observe while walking the dog, with another welter of random twigs. This welter is lit by a security light on a building, which casts shadows on the tree's fairly white trunk. I don't have a photo of this one, it's not very photogenic despite being technically interesting.

The shadows cast on the tree trunk are entirely horizontal. Perfect straight horizontal lines.

This took me somewhat longer to work out. The security light is in fact a horizontal row of LED lights. It is "big" in the horizontal direction and therefore, as it were, wraps around vertical twigs and eliminates their shadows. The light is "small" vertically, and so does not do the same to horizontal twigs. It is, in effect, filtering out verticality. Mathematically, there's probably a convolution somewhere in here.

This led me to think a bit about strip lights. We often see them talked about as a way to create interesting catchlights in portraits (a "cat's-eye" effect, with a vertical strip light on each side) or to rimlight things, or whatever. I don't think I've ever noticed a talk about how a strip light acts like a big light in one dimension, and a small light in the other.

In theory, you should get hard shadow edges parallel to the strip, and soft shadow edges perpendicular to the strip.

This is a preliminary and not very successful attempt to illustrate the effect. I think my faked strip light isn't very good. Don't even ask. I rather like the picture, though.

Work in our labs proceeds.


Further lab work produces these two photos, which make the point.


  1. "An eminent philosopher among my friends, who can dignify even your ugly furniture by lifting it into the serene light of science, has shown me this pregnant little fact. Your pier-glass or extensive surface of polished steel made to be rubbed by a housemaid, will be minutely and multitudinously scratched in all directions; but place now against it a lighted candle as a centre of illumination, and lo! the scratches will seem to arrange themselves in a fine series of concentric circles round that little sun. It is demonstrable that the scratches are going everywhere impartially and it is only your candle which produces the flattering illusion of a concentric arrangement, its light falling with an exclusive optical selection. These things are a parable. The scratches are events, and the candle is the egoism of any person now absent-- of Miss Vincy, for example."
    George Eliot, Middlemarch, book 3, ch.27

    For years I was convinced I had read this passage somewhere in Virginia Woolf, but then rediscovered it, to my surprise, in Middlemarch. Knew you'd want to know that.


    1. What a marvelous statement of this phenomenon! I suppose I should not feel *too* bad that Eliot said it a little more poetically than I did.

      Thank you!

  2. What's the provenance of the jar? (I'm a sucker for photos of ceramics)

    1. There was in my neighborhood a craft store, opened in (maybe) 1976. Glad Bag was the name. They did all manner of ceramic knick-knacks and stuff, and I think they did some business in the "decorate your unglazed knick-knacks and we'll fire them in our kiln, pick it up next week" line.

      By the time I moved to this area, 6 years ago, the store had been long shuttered into an ambiguous, but never actually *open* state. There was an apartment upstairs, and the owner lived there, getting older and older, as the building fell into vague disrepair. She had local family, who presumably made sure she ate, but who did not particularly tend to the building.

      Last year, Gladys died. Her sons spent a month or so clearing the place out for sale. As you can imagine, a craft store open for 30+ years and then just not opened one morning, has a lot of random shit in it.

      At one point they set up a shelf outside, with some of the crap they could not otherwise dispose of, but which seemed "good enough" that someone might want it. There is a lot of this in Bellingham. People are very optimistic about what other people might want.

      This little container was on that shelf.

      In short, its origins are roughly as thoroughly buried as can be imagined, but there's a story, anyways!

      It appears to be glazed, so I do not think it was intended for further "crafting" but I dare say it was the last of some batch of knick-knacks ordered and sold but for one, decades ago.

      There are no markings on it, at all. The whole is perhaps 4 inches tall, and feels in the hand like porcelain. Light, almost as if made of paper. It is rather clumsily made, you can see a certain blobbiness and lack of care in the photos, and this carries through to the interior.

      Nevertheless, it's obviously a very appealing little piece. The proportions, color, and material are good, striking, and beautiful.

    2. Presumably slip-cast and removed from the mold too soon, causing it to slump slightly out of true. White, low-fired bisqueware (non-vitreous) with (likely) lead glaze, cone 04-06. You could bring out the crazing by rubbing ink into it, if so inclined.

      I lived and breathed ceramics (mainly high-fired stoneware) from age 14-25, back for seconds 1986-1990 before I went into design. Had a business with my mom, built our own gas-fired kilns and everything!