Wednesday, March 4, 2015

Where physics and art dissagree

I was chatting with a friend about the color temperature of light. It brought to mind a post from 2012:

When I started to think about the text for this post, the thought came to mind of starting it with, “It’s always pleasant to go for a stroll on Dogbar Breakwater.” Well, that isn’t always the truth. It can be rather nasty out there. But that was not the case yesterday. It was a pleasant 45F, calm and sunny.
©2012 Steve Borichevsky
This is the typical picture that one would get, shooting straight down the breakwater to the light. But unless we were doing a study in brown grass, this shot is not very interesting. Let’s see if we can play a bit. The sun is going down, maybe we can get some colors.
©2012 Steve Borichevsky
As the sun sets, the shorter wavelengths get scattered out by the dust and water vapor that the light travels through. The result is the color temperature gets warmer, meaning that the colors shift towards the yellows and reds. The artist's concept of color perception of red being warmer and blue being colder just adds a layer of confusion to my universe.
©2012 Steve Borichevsky
You see, I was trained as a physicist. In physics, the blue end of the spectrum has a higher temperature and the red end of the spectrum represents a cooler temperature. Here’s why. When you heat an object to the point is starts glowing it will start emitting predominately red light. If you keep heating it up, it starts glowing more towards the yellow and then as it gets hotter, it is starts glowing white. But if you look at the intensity of the colors, as it heats up the brightest color peak shifts from red (cool to a physicist) to blue (hot to a physicist). If you have an light bulb on a dimmer switch, you can observe this for yourself. In a dark room, bump up the dimmer switch until the filament starts to glow, them back it off a bit. You’ll see it glow cherry red. Then increase the voltage, and it will shift towards yellow.
©2012 Steve Borichevsky
In astronomy, we classify stars by color temperature. You may have heard of a Red Dwarf, which is a small, cool star. Our star, the sun, is a medium sized star and emits predominately in the yellow. There are some massive, hot stars that emit predominately blue.
©2012 Steve Borichevsky
So anyway, the blue light gets scattered and the red light passes through. It has to do with the size of the wavelength of the light and what is between the sun and the observer. The light is scattered by stuff that is the same size as the wave length. Longer wavelengths pass through. Thus the direct light is more red (such as the that shining on the tower above) and the indirect light (the light from the sky above) scatters down and is more blue.
©2012 Steve Borichevsky
So what’s this got to do with this photo shoot? Uh, nothing.
©2012 Steve Borichevsky
I’m just apologizing up just in case you end up riding in a car with me and ask me adjust the air conditioning because it is too hot and I turn the dial towards the red. I think like a physicist, not like an artist. Red is cool, blue is hot. Just sayin’.

3 comments:

Margaret Adamson said...

Thanks for all the explanation of the red and blue issue. I had heard that before although it is over my head!! The evening light on these shots make all the difference to the beauty f them.

Merisi said...

Never take anything for granted, especially the color of light! ;-)

No matter the color temperature, Lord Kelvin surely would have loved those pictures as much as I do!

Roy Norris said...

My brain hurts now.{:))

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