Eclipses and Decibels

Re:Eclipses and Decibels by ctdonath on Monday August 28, 2017 @02:20PM (#15118840)

Yup, it's a "had to be there" thing. Complete eclipse, start to finish, took 3 hours. Totality was just over 2 minutes. Most of the time, lighting can only be described as "odd" - as you put it, color balance of full sunlight for brightness of sunset. Bugs & animals picked up on it, rapidly heading into night mode. Humans tended to stand around slowly realizing "huh? that's odd". Lighting starts as a sense of just wrong. Then at about 95% totality (!) you finally perceive the rate of change, as it exponentially plunges into darkness. Then you realize the darkness isn't, you're seeing with the visibility of a nightlight (but color balance still that of full sunlight), and proceed to freak over the visibility of the corona surrounding a big, well, black hole where the sun was. The horizon is also oddly bright.

And yes, there's a huge difference between any perceivable percentage away from totality, and totality itself. We're talking fractions of a second making a difference between direct viewing vs rapidly going blind.

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Re:Eclipses and Decibels by dredmorbius on Monday August 28, 2017 @03:46PM (#15119476)

NB: The colour-balance of night, say, under a full moon, is actually pretty close to that of daytime.

It's just ... well ... a lot darker.

Shooting long-exposure slide film is a good way to confirm this (no colour adjustment possible).

Moonlight is has a slightly lower (that is, optically "warmer") colour temperature -- 4100K rather than 5000K.

Contrast with "daylight" vs. "tungsten" film colour balance: 5500K vs. 3200K.

https://physics.stackexchange.com/questions/244922/why-does-...

http://www.apogeephoto.com/white-balance-and-color-temperatu...

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Re:Eclipses and Decibels by nkrisc on Monday August 28, 2017 @04:02PM (#15119596)

A lot darker, indeed. I recall camping in the mountains near Vail, Colorado many years ago during a full moon. It almost felt like day, but with a black sky. It was quite surreal. My immediate surrounding were illuminated (everything cast a distinct shadow) but everything just beyond your immediate vision was in darkness.

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Re:Eclipses and Decibels by Florin_Andrei on Monday August 28, 2017 @08:48PM (#15121359)

> Shooting long-exposure slide film is a good way to confirm this (no colour adjustment possible).

Or shooting long exposure with a digital camera that does not automatically adjust the color balance. E.g. take the raw data from the sensor, instead of a camera-generated JPEG.

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Re:Eclipses and Decibels by dredmorbius on Monday August 28, 2017 @10:59PM (#15121809)

Right. I was also contrasting _print_ film (negative process) as virtually all film-development would attemtp to "correct" shots for exposure and colour balance.

(Much of my experimental night photography was conducted ... some time ago.)

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Re:Eclipses and Decibels by Florin_Andrei on Tuesday August 29, 2017 @03:03PM (#15126767)

Hey, I did some of that too. Had my own little dark room and everything.

Working with film was, um, exciting? Not sure if that's the right word. Anyway, mistakes were final. I remember deliberating on the settings for a really long time before pushing the button.

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Re:Eclipses and Decibels by Florin_Andrei on Monday August 28, 2017 @03:08PM (#15119188)

Color balance does shift a bit towards red when it's close to totality. I've picked it up visually (it's a small change), and the camera also confirms it:

https://www.youtube.com/watch?v=af0dQLdmhxs

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Re:Eclipses and Decibels by peeters on Monday August 28, 2017 @08:26PM (#15121249)

Why is it so much warmer immediately after totality than immediately before? Seems more like the camera shifted its white balance over the course of the video.

Thanks for sharing though! I wasn't able to experience the full eclipse so I love seeing others experience it.

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Re:Eclipses and Decibels by Florin_Andrei on Monday August 28, 2017 @08:44PM (#15121338)

The camera's white balance definitely did shift.

To my eyes, close to totality (on either side) the light was a bit redshifted. Not much, but a little. The change seemed symmetrical before and after.

I've imaged the whole event. Looking at the disk of the Sun, the color is not the same everywhere. The edge definitely loses energy in the blue end of the spectrum - I believe for the same reason why blue light is dispersed more, compared to red, in Earth's atmosphere. So near totality, when you receive light only from the edge of the photosphere, it's normal that the spectral composition looks different.

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