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Showing posts from September, 2007

High Dynamic Range

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Exposure values or EVs are numbers that refer to combinations of lens aperture and shutter speed. Your eye is capable of discerning 12EV but a typical camera can only handle about 6.

So?

So if you shoot the same image at a range of speeds and sandwich them together you can see a higher dynamic range, one closer to what you're used to seeing with your eye. Photoshop has a handy tool that will help combine multiple images, and there are several stand-alone programs to help too.

Here's a shot properly exposed for the tree trunk (click any image to enlarge):


There's 4.0EV difference between the black, dark tree trunk and the bright, white surf and clouds behind. Here's the shot combined with a properly exposed beach (Kauai HI).


There are a few artifacts that give away the fact that more than one images is involved: note the branches at the top that were moving in the tradewinds. If there are moving people or cars in one of the shots they'll look ghostly.


This picture, taken …

Was St. Augustine psychic?

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St. Augustin, you may recall, was the first archbishop of Canterbury, and was considered the Apostle to the English and a founder of the English Church. [Yike! No he wasn't, as a sharp eyed reader noted in the comment below. Mea Culpa, wrong Saint Augustine. The right one was 200 years earlier (November 13, 354 – August 28, 430) and was one of the most important figures in the development of Western Christianity, and considered to be one of the church fathers. He framed the concepts of 'original sin' and 'just war'.]


About 1400 [make that 1600] years ago he wrote:

"Usually, even a non-Christian knows something about the earth, the heavens, and the other elements of this world, about the motion and orbit of the stars and even their size and relative positions, about the predictable eclipses of the sun and moon, the cycles of the years and the seasons, about the kinds of animals, shrubs, stones, and so forth, and this knowledge he holds to as being certain from re…

Can Moonbeams Heal?

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Oh puh-leeze.

Must be a slow news day. CNN is touting, front page, an old story from a local TV station in Tuscon that breathlessly reported there's an outfit in Arizona selling moonlight as a cure all.


The piece starts, "Conventional wisdom says that whenever there's a full moon, strange things happen." Right off the bat you know this is gonna be a crock. Or at least you know that if you understand that 'conventional wisdom' is generally wrong—and definitely wrong in this case.

Conventional wisdom had it that the Sun rotates around the earth, remember. Come to think of it 20% of the people in the U.S. still do. Conventional wisdom, for that matter, used to be that Thor made thunder, although that might more rightly be called religious 'wisdom.'

Why can't people get it through their heads that you can't believe everything that comes into it. "Don't believe everything you think," as the bumper snicker says.

The CNN report goes on sagel…