Thursday, June 4, 2009

Continuing Adventures

While my feelings about Nikon's sales and marketing and how they crippled the D60 haven't changed, I have discovered some work-arounds that make my garage sale lenses useful. But first I'll discuss the optical characteristics of the two lens. They weren't what I expected.

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.

A rule of thumb is to close the iris about 2 stops to photograph at the sweet spot. The down side of doing that is you are using only a quarter of the light gathering power of the fast lens you paid good money to buy. A problem? Depends. When it come to camera optics (and ISO setting and Depth of Field and ....) good photography is always a series of compromises.

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.

Even a disposable camera I once bought for $12 and tore apart to modify surprise me with a four element lens. Since all the pieces fell out on the table, putting them back together in the proper order and orientation was a bit of a challenge.
For this test I took a series of five or six photos spaced a stop apart with each lens.

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.

Back in the 1980's Vivitar wasn't noted for high quality amateur optics. The company imported all its lens and, business being business, bought and sold them as cheap as possible. You get what you pay for.

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.

After that success--time for a field trip. Without a tripod

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

And since we are using an antique lens, what would be more appropriate that to convert it to black ane white.


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