…and HDR

Double click for a larger image...
Double click for a larger image…

High-Dynamic Range imagery is pretty amazing.  The idea behind it is relatively simple and has to do with the difference in the ability to perceive light by the eye versus the camera.  The human eye is a true miracle and the iris of the eye and brain work together to constantly adjust the amount of light that enters the eye.  Cameras, on the other hand, can’t do that.  They take one image and the exposure is frozen – not to mention that the human eye can distinguish between a MUCH wider range of light and dark simultaneously than any camera.  Perhaps you’ve seen photos where the sky is “washed out” – there is no blue and it’s just whiteish.  That’s because of the problem your camera has in apprehending a wide enough range of light.  In the case I just described, the light sensor in the camera took a meter reading off of a darker area and tried to brighten the image. Or, if you focused on a lighter area, the dark areas of the image may be lacking detail because they are too dark because the camera darkened the image.

The technique behind HDR is simple: shoot more than one version of an image.  Typically, at least three will be used (one that is intentionally underexposed so the lighter areas are not “washed out” [all whitish like the sky], an exposure that the camera thinks is correct, and another that is overexposed so the darker areas have more detail).  Then, typically using computer software with sophisticated algorithms, the computer combines the three images into one, keeping the darker portions of the image from the overexposed photo and the lighter portions of the image from the underexposed photo and the “normal” exposure.  The result is a HDR image.

Some HDR images are garish and look very fake, while others are truly beautiful and come much closer to capture an image that is closer to what the human eye sees.  I don’t typically care for the surreal HDR images, but a “realistic” HDR image can be lovely.

One more thing about HDR images: they typically aren’t used for images where things are in motion because the images have to be aligned carefully or you get “ghosting” from movement.  For that reason, it is best to use a tripod when taking HDR images in order to minimize camera shake that would tend to blur any image.

Today’s photo was shot last Friday at Mission Springs Conference Center in Felton, CA.  It is the result of three exposures…handheld, actually.  I’d not really tried HDR images with flowers before and there was a slight breeze, but the image still turned out nicely (at least, I think so).

ON THIS DAY IN HISTORY:  in 1934, a massive storm sent millions of tons of topsoil flying from across the parched Great Plains region of the United States as far east as New York, Boston and Atlanta.

When the Great Plains were settled in the mid-1800s, the land was covered by prairie grass, which held moisture in the earth and kept soil from blowing away even during dry spells. By the early 20th century, farmers had plowed under much of the grass to create fields. The U.S. entry into World War I in 1917 caused a great need for wheat, and farms began to push their fields to the limit, plowing under more and more grassland with the newly invented tractor. The plowing continued after the war, when the introduction of even more powerful gasoline tractors sped up the process. During the 1920s, wheat production increased by 300 percent, causing a glut in the market by 1931.

That year, a severe drought spread across the region. As crops died, wind began to carry dust from the over-plowed and over-grazed lands. The number of dust storms reported jumped from 14 in 1932 to 28 in 1933. The following year, the storms decreased in frequency but increased in intensity, culminating in the most severe storm yet in May 1934. Over a period of two days, high-level winds caught and carried some 350 million tons of dust all the way from the Great Plains to the eastern seaboard. According to the NY Times, dust “lodged itself in the eyes and throats of weeping and coughing New Yorkers,” and even ships some 300 miles offshore saw dust collect on their decks.

The dust storms forced thousands of families from Texas, Arkansas, Oklahoma, Colorado, Kansas and New Mexico to uproot and migrate to California, where they were derisively known as “Okies”–no matter which state they were from. These transplants found life out West not much easier than what they had left, as work was scarce and pay meager during the worst years of the Great Depression.

Another massive storm on April 15, 1935–known as “Black Sunday”–brought even more attention to the desperate situation in the Great Plains region, which became known as the “Dust Bowl.” That year, as part of its New Deal program, FDR’s administration began to enforce federal regulation of farming methods, including crop rotation, grass-seeding and new plowing methods. This worked to a point, reducing dust storms by up to 65 percent, but only the end of the drought in the fall of 1939 would truly bring relief.

TRIVIA FOR TODAY:  Osteoporosis fractures cost around $18 billion per year, or $38 million a day. In 2005, fractures related to osteoporosis were responsible for an estimated $19 billion. By 2025, experts predict it will rise to $25.3 billion.


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