Just what is Alpenglow?

Just what is Alpenglow? I do know that it is the pink light you see

on the mountain peaks. Galen Rowell had many great photos like that.

What I am wondering is the pink or red showing on lower non-snow

covered mountain at a lower elevation, say 1400 feet also Alpenglow?

What about the pink light on clouds. Is this also Alpenglow? I am

referring to this pink coloration under a clear sky with high

visibility and the sun not shining through clouds.

 

I do not see this term used in meteorology which I find somewhat

puzzling. Perhaps the term is only used by nature photographers and

artists. Dictionary.com mentions it as a rosy glow on snow-covered

peaks at dusk or dawn on a clear day. Is this definition correct?

alpenglow \AL-puhn-gloh\, noun:<br><br>

A reddish glow seen near sunset or sunrise on the summits of mountains.<br><br>

You might also try clicking <a href="http://en.wikipedia.org/wiki/Alpenglow">here</a>

I think the German term is Abend Sonnenschein, or evening sunshine...which I interpret as dusk. IMHO alpenglow is the reddish spectrum of sunlight reflected by an object arising from the surface of the earth (like a mountainous peak, rock outcrop, etc) shortly before sunset, the reddish color caused by absorption or scatter of the blue spectrum due to the light passing through more atmosphere. Why would it be puzzling that meterology doesn't use the term? Science doesn't necessarily follow the vernacular idiom.

The defining quality of alpenglow isn't the result (beautiful, reddish light) or locale (mountainous environs) so much as the cause. In the strictest sense it is a diffused and indirect illumination (via refraction due to moisture and reddish-colored from pollutants in the atmosphere) rather than DIRECT light from an almost-set or just-risen sun. It often occurs just before sunrise or just after sunset, thus precluding direct light. Consider the word 'glow' for a moment, which denotes 'light being emanated from' rather than 'illuminated by' an external source. Without direct light from the sun that is below the horizon, the mountain seems to be inexpliably 'glowing from within'.

 

The word has a romantic flavor, thus encouraging its misuse to refer to any reddish/golden light as alpenglow. It's not an everyday occurrence (whereas the direct, golden light at sunrise / sunset is) and is reliant on proper atmospheric conditions. German origin: alpen + glühen.

Alpenglow; it wouldn't surprise me a bit if it was Galen Rowell's use of the term that popularized the word among photographers, namely to describe the reddish glow that would appear on the snow-crested Alps. Taken in a more common context, I describe alpenglow to people as the red and pink colored light that appears at either sunrise or sunset. <br>

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The reddish color lightwaves are the longest in the visible spectrum of electromagnetic energy. Of all the visible lightwaves, they also move the slowest. Light that has to travel through more atmosphere has most of the blue absorbed, so the slower red waves of color are actually the only ones that make it through to our eyeballs. As the sun sets (or rises; reverse the process) you can see a gradation of color rise in the eastern sky, pinkish red onto of blueish purple. As I actually once explained to Galen - this transition of color is really our horizontal view of the Terminator Line, which is the line between day and night that the space shuttle astronauts would see when looking down (vertical) on the planet. (It was a big deal to be able to know that I taught him something, however small, albeit thanks to my interest in astronomy.) The pinkish red light is actually sunset light that continues to rise in the sky as the sun dips below the horizon. The blue purple light is actually the shadow of the earth also rising into the sky. Mountains get the most red light since they are higher, but that same ligh can also light the underside of clouds after the sun has already dipped below the horizon. <br>

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Yes, you can see alpenglow at lower elevations including sea level. The primary difference is the amount of time that red light will be distinctly visible, before transitioning to a warm golden, or yellow light. When I did my book on San Francisco, I purposely shot the TransAmerica Pyramid as if it was a mountain peak. The red light did show on the building, but it didn't last for more that 2 minutes. In the Eastern Sierra, you can watch the transition form pink to red to gold take over ten minutes or more. Again, the differnce in time that the effect lasts is totally related to the amount of atmosphere the light needs to travel through.<br>

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The San Francisco image is <a href="http://www.enlightphoto.com/webpages/caba1/ba2_03.htm">Here.</a> <br>

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One of my favorite Yosemite alpenglow images is <a href="http://www.enlightphoto.com/webpages/cayos/yos3_13.htm">Here.</a>

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Finally, I hate to dispute with Lilly, but Alpenglow is still very much a form of Direct light. If you stood on a moutaintop bathed in alpenglow, you would see the sun. <br>

<br>

Gary Crabbe<br>

<a href="http://www.enlightphoto.com">Enlightened Images</a><br>

<a href="http://www.enlightphoto.com/views/">Enlightened Images Views</a>

Here is one.<div></div>

This one too.<div></div>

I can't explain alpenglow scientifically like some others here, but I do know it sure as heck looks impressive.

<a href="http://www.rwongphoto.com/RW944.html">Sierra Wave over McGee Creek, Eastern Sierra, California - 2005</a>

</p>

California stock photography, fine art prints, photo blog:<br>

<a href="http://www.rwongphoto.com">www.rwongphoto.com</a>

...and this is my favorite. The original slide looks a lot better than this scan.

 

Mary

It's one of those things I can't define, but this thread gives me the opportunity to shamelessly post one of my favorite examples of it.<div></div>

Silly me I thought it was a breakfast cereal :) ( Sorry I could not resist. )

 

However I have learnt something but have a question - does atmospheric pollution not have an effect sometimes ?

 

Impressed by the images.

Actually it is Alpengluehn (i think the rest of the world cannot display the single letter for "ue" we have here in Germany, it is a u with 2 dots on top) which means the same as Alpenglow.

<I> Of all the visible lightwaves, they also move the slowest.</i><P>

 

Don't think so -- unless you're trying to tell us that the speed of light varies with wavelength.

Perhaps he meant "vibrates" the slowest - longer wavelength/lower freq -> lower energy? (not sure if this is directly related to the described phenomenon - I had thought it was more a prism-esque scattering). Last time I checked, you had to do something <a href="http://www.news.harvard.edu/gazette/1999/02.18/light.html">more impressive</a> than put a red gel over your flashlight to slow the light down. ;-) Nice site/blog though Gary and pictures all.

<I>you had to do something more impressive than put a red gel over your flashlight to

slow the light down</i><P>

 

The speed of light does vary with the medium through which it is traveling -- the well-

known value of ~ 300,000 km/sec is what occurs in a vacuum. In denser media (such as

air, water, glass lenses, etc.), it does slow down relative to vacuum speed. <P>

 

I'm no atmospheric physicist but I think the usual explanation of the red color shift in

sunrises and sunsets is 'simply' a filtration effect -- shorter wavelengths (blues, etc) are

more scattered, absorbed, etc. when passing through a thick layer of atmosphere than are

long wavelengths (reds). It's not a function of different wavelengths traveling at different

speeds.

>Alpenglow is still very much a form of Direct light. If you stood on a moutaintop bathed in alpenglow, you would see the sun<

 

Gary, are you sure this is true? I've made many photographs with the sun long gone. I can recall memorable sunsets a few weeks after the eruption of Mt. Pinatubo, when a red glow suffused the high country well into twilight; in fact, the effect was visible on film, even though the human eye could no longer discern the warm color.

 

Is is possible Alpenglow can occur in both direct and indirect light?

Or is the faded light something different from classic Alpenglow?

Just FYI: The OED defines alpenglow:

The rosy light of the setting or rising sun seen on high mountains.

It gives the earliest use to John Tyndall's Fragments of science for unscientific people from

1871: "On August 23, 1869, the evening Alpenglow was very fine."

Technically, alpenglow is a very specific thing: shortly after the sun has set, sunlight may reflect from a bright reflective surface such as snow or ice (and sometimes water or sand) which is beyond the horizon, back up into the atmosphere.

 

<P>

Searching on google images, I found a <A HREF="http://www.tobinphoto.com/images/photos/alaska-alpenglow.jpg">perfect example</A>. Note that there is no direct sunlight in this photo, not even lighting the clouds.

 

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It appears that the term is being aggressively redefined to mean merely: low angle, reddish direct sunlight. This is unfortunate, as true alpenglow is a somewhat rare and unique form of light.

OK: I'm Busted. Yes, I meant red light was of lower frequency wavelength. Not Slower than the speed of light. When I meant slow, I was referring to the timing interval between wavelength peaks.<br>

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But, yes, I am also sure that Alpenglow is a form of direct light. Even though the sun has set from YOUR vantage point the light of the sunset continues up into the sky. Imagine watching a shadow move up a mountain. The line where the shadow starts has direct light above it. Once the shadow reaches the top of the mountain, the light just doesn't "Turn Off" like a light switch. The sun and shadow continue to move upwards into the sky. You can mimic the effect with a penlight, tennis ball, and your finger to represent the sun, (Curved) earth, and a mountain. <br>

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Michael: I wish I could see your perfect example, as all I got was bear eyes. What you are referring to may happen, but I don't think it is alpenglow. Esp. since it sounds like you'd have to be facing the setting sun, looking toward that direction of where something bright is below the western horizon. Alpenglow is usually seen when facing away from the rising or setting sun. Frankly, I think you have it a bit backwards, in that Alpenglow is relatively common, but what you describe is more like a rare phenomenon. Just like a Specter of the Brocken is a type of rainbow, it is very rare and requires specific conditions. It wouldn't typically be referred to as an ordinary or common rainbow. But please, if you do find more info, post away. I really want to see that picture.<br>

<br>

Gary Crabbe<br>

<a href="http://www.enlightphoto.com">Enlightened Images</a><br>

<a href="http://www.enlightphoto.com/views/">Enlightened Images Views</a>

Micheal: Blame the lack of caffine, but I did see the photo, not by clicking the link, but by copy & pasting the URL. Weird. Anyway, Your picture is a classic example of what I said in my first post. That's the horizontal view of the vertical terminator line, or in simple terms, the earth shadow. The blue light is the earths shadow rising up into the sky as the sun sets. The upper (red / pink / purple) sky is NOT light reflected off anything, but is 100 driect sunlight, passing through so much atmosphere that it's color has shifted dramatically. If you stood on a ladder high enough to be above that blue line, you would see the sun. Guarenteed. <br>

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I gotta admit, I was a tad let down seeing this photo. I was all set to see some totally cool and rare optical phenomenon, and instead wat I got was the most common thing of all, happening twice a day for the last 4 billion years. The earth shadow rises in the east at sunset, and sets in the west at sunrise. If you don't believe me, go out any clear morning 40 minutes before sunrise, face west, and watch what happens. You'll see exactly the same light in the sky, minus the mountains. <br>

<br>

Gary Crabbe<br>

<a href="http://www.enlightphoto.com">Enlightened Images</a> <br>

<a href="http://www.enlightphoto.com/views">Enlightened Images Views</a>

Dave: Yes I'm sure. Imagine the sky at sunset is a two-toned umbrella. The half that is pink / red is direct sunlight, then below that is a blue half in shadow. When the sun sets, all the umbrella (sky) is pink. As the sun sets further below the horizon, imagine tilting the umbrella tip toward the setting sun, moving up and west at the same rate the sun sinks in the west (because the earth spins east). The blue part of the umbrella rises in the east, and the pink part moves higher in the sky, up and over the zeinith, until the last remanents of direct sunlight (glow) sets in the west. <br>

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You are also right that film is more attuned to rendering that than our eyes, especially saturated films like velvia. But it is the light from the pink part of the umbrella that is still providing the light on the landscape. <b><a href="http://www.enlightphoto.com/webpages/utZion/zion211.htm">This picture</a></b> shows a perfect example of the glow 20 minutes after sunset still providing a good deal of light, but it also required a 30 second exposure to get it all on film. With Mt. Pinatubo, the ash helped make the red light more intense, by scattering and absorbing more of the blue. But the red was still direct light. Just picture a straight line from the <b><a href="http://www.enlightphoto.com/webpages/portpg1/sierarod.htm">red glow on the bottom of a cloud after sunset (or before sunrise)</a></b> to the sun below the horizon. There's no snow or water or ice in my photo, so the red light has to be coming from somewhere; there's no relection, so by default the that bright red light must be coming directly from sun. And again, if you were on a ladder at the same level as those clouds, you would see the sun. Guarenteed. It takes a much greater mass than the earth to warp gravitational space enough to bend lightwaves.

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Hope that all helps everyonne.

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<br>

Gary Crabbe<br>

<a href="http://www.enlightphoto.com">Enlightened Images</a><br>

<a href="http://www.enlightphoto.com/views/">Enlightened Images Views</a>

Being doublely shameless here. So let me guess. </p>

 

Earth Shadow: <a href="http://www.rwongphoto.com/RW1300.html">Low Tide and Sea Stack at Dusk, Corona Del Mar, California</a> </br>This image was shot when it was almost totally black outside and there wasn't much color visible to the eye but the 30 second exposure brought the color out.</p>

 

Alpenglow: <a href="http://www.rwongphoto.com/RW531.html">Crescent Moon Sunset over Daly City, California</a> </br>This was shot just after the sun had gone down.</P>

 

<a href="http://www.rwongphoto.com">www.rwonghoto.com</a>

<I>. This picture shows a perfect example of the glow 20 minutes after sunset still

providing a good deal of light, but it also required a 30 second exposure to get it all on

film. With Mt. Pinatubo, the ash helped make the red light more intense, by scattering and

absorbing more of the blue. But the red was still direct light. Just picture a straight line

from the red glow on the bottom of a cloud after sunset (or before sunrise) to the sun

below the horizon. There's no snow or water or ice in my photo, so the red light has to be

coming from somewhere; there's no relection, so by default the that bright red light must

be coming directly from sun. </i><P>

 

I don't think this example shows direct sunlight, if by 'direct' you mean a photon traveling

in a straight line from sun to Earth would hit Checkerboard Mesa, or that someone sitting

on top of Checkerboard Mesa could still see the sun. If you took the photo 20 minutes

after sunset, the sun was about 5 degrees below the horizon (the sun "moves" through the

sky at 15 degrees per hour). That's ten solar diameters below the horizon. Put it another

way, at that time the sun would be setting about 300 miles to the west (sunset moves west

at about 1,000 miles per hour at the equator, and at decreasing 'speed' as you go to

higher latitudes). <P>

 

I can't do the math in my head, but you would need to be many tens of miles above the

Earth's surface to get direct sunlight at that time. The red light in your image was coming

from the sun, but not directly; it was scattered through the atmosphere "around" the

horizon; so much of that light is lost that you needed an extremely long exposure to

record the scene.

Mark:<br>

<br>

Sorry, I may not have been clear. The checkerboard mesa shot was lit by the <br>reflected</b> glow of the pink umbrella of light high in the sky after sunset. The pink glow is <b>caused</b> by direct light, but it is acting just like an umbrella that you would see in a photo studio.

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The bright red light on the clouds in the dirt road photo is direct light caused by photons travelling in a straight line from the sun.

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Richard: In reverse order, right, & wrong. The light on the cloud with the crescent moon is alpenglow, or direct light from the sun. If I assume you are facing west at sunset then your first guess was wrong. That blue line is not the earth's shadow, but rather a layer of coastal clouds (fog) hanging well offshore. The light in the sky is caused by direct light going upwards from the sun below the horizon, and hitting the dust in the atmosphere. If this had been taken not long after Pinatubo, that pink glow would have been dramatically more red.

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<br>

Gary Crabbe<br>

<a href="http://www.enlightphoto.com">Enlightened Images</a> <br>

<a href="http://www.enlightphoto.com/views/">Enlightened Images Views</a>

Mary:

 

** applause **

 

Do you live near Denali or were you just lucky enough to get those not-a-cloud-in-the-sky shots on a short visit?

 

Be well,