Saturday, June 7, 2008

Annular Highlights

When you look into the maze of bare branches of a forest in winter, you’re only seeing a fraction of the detail. The light illuminates only a few of these ice-covered branches. Most of them blend invisibly into the general gray.

Which of the smaller branches and twigs catch the highlights? Only those that are oriented 90 degrees to the direction of the light. The illuminated twigs align into concentric rings around the centerpoint of the light source; hence I’ve named the phenomenon “annular highlights.”

The three arrows in the photo are placed perpendicular to the illuminated twigs. If you follow the arrows, they lead to the location of the sun.

Annular highlights can also be observed in the scratches of a well-used stainless steel surface, like this cookie sheet and pot lid. Look for it in the window of a passenger train on a late afternoon, in a cobweb on a dewy morning, in a cornfield lit by a setting sun, or on telephone wires on a rainy night.

9 comments:

Cully said...

I LOVE this affect. My favorite place to see it is looking at a streetlight through a winter-bare tree. I tried to explain this phenomenon to a non-artist friend once and they simply couldn't see it.

HorsePunchKid said...

Cully, I tried to take some photos of that phenomenon a while back, with limited success.

Katherine said...

Cobwebs on the grass at dawn. A great name for it... Did you coin it?

Jon Hrubesch said...

This reminded me of a different phenomenon that happens when my windshield wipers create smudged lines (equally distant) across my car window. At night the street lights will reflect off each of the smudged lines forming a long line of light similar to that found by looking at many puddles or waves on the water reflecting the same light source back to the eye. An effect that some lenses create, I assume, with concentric rings giving a star shape to a light source. Love all your posts James. I realize this is a little bit different than the phenomenon you were describing.

Moai said...

It's the little observations like this that make this blog so great. Thank you, James.

RocknOats said...

Holy Cow! That is the most amazing, "I would never have noticed that in a million years" tip I've seen! BTW, I'm a frequent visiter, I just don't write much. Love the books too.

Thanks for doing this!

René PleinAir. said...

It kept me thinking, but did you know that the star forming stripes are caused by the same principal, ... those are really the polish-marks on the glass that you see, ....when looking through some optical stuff, .... obvious

Katie said...

Hi, James, I'm coming here from your snow post today. Did you know that George Eliot wrote about this very effect in Middlemarch? She was a wonderful observer. My English Lit. professor picked out the passage and read it to us aloud as one of her favorite passages in the novel. Here it is:

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...

And then she goes on with her story.

Thank you for your wonderful blog, I have been enjoying it very much the last couple of days. Your little explanation of light--that all would be formless darkness without a specific light source--was a total "lightbulb" moment for me. You are also very generous with taking the time to check out your readers' work. Someday I'll post some. My favorites of yours are your plein air paintings of everyday places like the McDonalds' sign. Thanks again!

James Gurney said...

Katie, thanks so much for sharing that excerpt. It's great to know that others have noticed the same effect. I also found a reference to it in Minnaert's book. Thanks, too for your kind words.