Friday, June 26, 2009
Nine to ten thousand years ago the scene would have been different. The moraine marks the farthest push of the last of the glaciers that have scraped the Midwest flat. From the bottom of the kettle pond--formed when a ten acre glacial ice cube melted and the ground level dropped--to the top of the moraine looked to be about 400 feet. There had been a lot of ice here when mammoths and mastodons and saber tooth cats roamed the frozen tundra to the south.
So what, you might ask. The ice ages are over. Except in cute animated movies.
But the ice ages are NOT over. We are in an interglacial period--a period of warmth when the glaciers retreat north. Once there they begin to recollect snow and ice so they can advance south again. Then they hang around for a couple hundred thousand years.
Happened four times in the last million years. The basic causes of the glaciers--the earth's tilt and orbit, the heat output of the sun, and the routes of the ocean's currents that move or don't move heat from the south to the north--have not changed. So there is no reason to think that it won't happen again.
Quess what. Interglacial periods last an average of ten thousand years. And since the ice was here nine to ten thousand years ago--so it's about time to think of selling your Canadian fishing lodge. We might be in for a long cold snap.
Far fetched. Not really. Starting around 1400 Europe--the only northern area where anyone wrote about the weather--had its Little Ice Age. Glaciers moved down the Alps. Bad weather lead to famine and peasant revolts. Even the Thames river at London froze over solid for several weeks in 1815. Something that hasn't happened since.
1815, the start of the Industrial Revolution. Ever since then we have been dumping more and more CO2 into the atmosphere, trapping more and more heat from the sun and melting arctic ice at a rate never measured before. The great and evil global warming.
But what would have happened without global warming. Would the Little Ice Age be still with us--long bitterly cold winters, short growing seasons and a frozen Thames almost every year.
A contrarian position, I know. Not at all. political correct. But something to ponder as I sort through the images of moraines and kettle ponds taken on a hot hot day along the Ice Age Trail
Thursday, June 4, 2009
Of the five lens I now own that fit on a Nikon, one of the primes has a 50 mm focal length. Three others can be set to 5o mm or close to it. So an obvious first test is to mount the D60 on a tripod and take a series of pictures with each lens.
My target was the licence plate of my neighbor's car. It was parked about 125 feet from where I set up the tripod and the lines of the numbers and letters were a 1/4 of an inch wide. Resolving the lettering at this distance was reasonably tough challenge for the camera and lenses. My fifth lens--the 35mm prime--couldn't do it
The D60 has three focus boxes. As you can see from the full frame image I shot with the box on the left over the licence plate. Lenses are at their best in the center and I was looking for problems.
Why? you may ask. The individual elements (simple lenses) in your lens barrel have their own series of aberrations--spherical, coma and astigmatism--that blurs the focus The idea behind an optical design is that for every lens element that blurs the focus in one direction you add another lens element that blurs it in the other direction. Then you place the iris in the lens barrel where the focus will clean up when you close it. A simple idea in theory; a much more complicated problem in practice. Big buck pro lens can have up to twenty lens elements of varying types.
As you can see from the blow ups of the licence plates the f1.8 50 mm prime lens has a problem when it is wide open. The G looks more like an E and the W at the end is a blob.
But as I expected, the plate became readable when I stopped down the lens to f 2.8.
So the prime lens turns out not to be quite the cult classic lens that some on the Internet have claimed.
As for the other three lens. their images were readable at the iris openings I tested.
The big surprise was how sharp the thirty year old Vivitar 35-70 mm zoom was. The lens that I once thought might be only good for parts appears to be the big bargain.
With one exception. After some research I discovered that lenses with magic serial numbers, 28xxxxxxx, were made by Komine. Those folks turned out above average optics. And yup, my serial number is 28213560.
How above average is the lens? One way to work around the rangefinder problem (see the previous blog if I'm confusing you) is to mount the camera on a tripod and switch back and forth between the manual mode where the camera takes a image and the aperture mode where the rangefinder works.
What happened? The macro--or micro as Nikon calls it--photos are below.
At the lens's closest focus distance--15 inches-the long dimension of the area imaged is 110 mm. This works out to a 3:1 subject to image ratio using the full frame and old fashion 35 mm rules. Not the 1:1 ratio purists insist on ....but have you priced one of those babies?
When shooting studio still lives-- (How did an arrangement of the inanimate end up with that name? Still, yes . Live, no.) Back to the subject at hand. With my non live still lifes I can take longish exposures. The top photo is f2.8 at 1/125 sec. The one below it is f22 at 1/2 sec.
Love the control over the depth of field the lens gives me. It's a couple inches at f22.
What else could I do. Add a #3 closeup lens left over from my film days. That brings the long dimension down to about 70 mm for a subject to image ration of 2:1
And what about the 2X telephoto extender. Now we are down to 35 mm and at the magic 1.1 ratio.
So it's back to focusing basics. The lens has a focusing scale. I have a tape measure. The camera also has a little green dot the lights up solid what the area within the focus box is in focus. Even in manual mode. Nowhere as easy to use as the rangefinder but it's something.
Unfortunately, the dot is part of a servo system that doesn't servo. But if I and the camera are close to the correct distance and I rock back and forth, I can make the dot light up.
Occasionally. If I don't move too fast. And if the photo gods are giggling. I'm going to have to work on that technique.
Plus find a screwdriver that fits the tiny, tiny screw that holds the focusing scale in place. It has worked loose. The only thing holding it anywhere near its right place is the oval 'passed inspection' sticker.
But despite these problems, I did steal some images in my neighbor's flower garden