How to snap a green flash

Q: I saw the green flash twice this winter. Very, very cool! I tried to get a photo of the second flash but my digital camera (Olympus D460, no filters, telephoto lens zoomed in) couldn't seem to capture the green. Do you know why not? Like many digital cameras, there is a short delay between the time I push the button and the camera snaps the picture. The second flash, however, seemed long enough to catch, even with a delay.  Chris, Florida

A: Vivid pictures of the green flash aren't easy to take. Green flashes happen quickly: a fraction of a second to, at most, a few seconds. A green flash is a phenomenon where the atmosphere, acting as a prism, bends the Sun's rays. This causes the top edge of the Sun to turn green, for a moment.

Taking a green-flash photo isn't easy.  Photo courtesy of Norm Vargas and Alex Bogdanovich, copyright, used with permission.

Here's advice from a couple of experts:

Lu Rarogiewicz, astronomer and weatherman at Mount Wilson, has this to say on the subject: "It's extremely difficult. I've taken hundreds of pictures of the green flash and only a few percent caught the green just right." The exposure has to be "smack on the mark." You've got to outfox the exposure meter, which averages light over a large area of the scene to arrive at any given 'exposure.' The exposure meter, consequently, dictates too wide an aperture to catch a green flash. After all, you are taking a picture of the Sun.

He suggests that you wait until the Sun is about 98% set. Aim your exposure meter at the top of the Sun and get a reading. This gives you an estimate of the proper exposure for the green flash. The later-occurring flash will be dimmer. So, double or quadruple the aperture opening by increasing the exposure setting one or two stops. Work quickly.

It's a trial and error procedure. Look at your picture and figure out how to change the exposure setting for the next snapshot. Unfortunately, you probably can't work fast enough to take another picture of this green flash.

Norm Vargas, amateur astronomer and board member of the Los Angeles Astronomical Society and the one who took the photo shown above, emphasizes magnification: "I would say that Chris' [the questioner's] attempt to image the green flash may have been hampered by the digital camera's lack of magnification. Even fully zoomed, a digital camera doesn't have the long telephoto capability of a 35 mm system. You can try putting the camera up to the eyepiece of a telescope to get the magnification you need, especially if there is an LCD screen on the camera that lets you see the image as you take it." He suggests a strong telescope mount or tripod to minimize camera shake.

Norm also mentions a strange eye effect. "As one intently watches a sunset, the color balance of the eye/brain system becomes shifted towards the blue end of the spectrum as the eyes try to neutralize the yellow or orange of the sun. When the disk of the sun is almost gone, the orange and yellow have faded, but the blue shift within the eyes remains and the sun looks greener than it really is."

Norm describes (see Further Surfing) how he took the picture depicted in the figure and ends with "good luck to all."

(Answered July 5, 2002; updated Oct. 23, 2007)

Further Surfing:

Norm Vargas: How Norm took the featured photo

WeatherQuesting: The green flash

Andrew Young, San Diego State U: Intro to green flash

USATODAY.com: Scattered light brings blue skies

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