As I mentioned in an earlier post CPM has moved. On the last weekend in the old building they held a garage sale to get rid of what they didn't want to cart away. Among the goodies was an ancient 500 mm Cambron lens that I remembered seeing for sale at an earlier fundraiser.

The Cambron name is not synonymous with quality, but the bigger problem was the oddball bayonet mount that fitted some equally oddball camera of the 1970's. (a Kiev perhaps) So I moved on to buy other things--lightstands, a photoshop book and a Nikon enlarger lens that may make an excellent UV lens if it turns out not to have a coating that blocks UV.

After I'd gone home I had an idea. As a lens the Cambron may have been useless but if I removed the front lens element it might work as an achromatic close up lens. This idea became even more appealing when, after some Internet research ,I discovered the lens was actually a relabeled Tamron--a lens maker noted for its excellent optics.

So I went back over to CPM on Saturday, saw that the lens was sitting where I left it, and came home with my very inexpensive prize. Turns out I was the only customer that showed up that morning and it was, 'you want it--name a price" day.

Later when I was trying to decide if I should borrow or buy a spanner wrench to remove the lens retaining ring or do a cheapie and take a hacksaw to the barrel, I happened to give the oddball bayonet mount a good twist. To my great surprise it loosened slightly and then unscrewed off. I had bought a T-mount lens!

Tamron was and still is a manufacture of after-market lenses. They had invented the T mount forty odd years ago. No matter what brand of camera a prospective customer owned all the salesman in the camera store had to do was to screw on the proper mount to make what was then a $250-300 sale. And all I had to do was get on ebay, buy a Nikon mount, and up my total investment to $15. Love those garage sale lenses.

Warning--at first I thought it was a M42 lens and almost ordered that adapter. The T mount has the same diameter (42 mm) but has a .75 mm thread pitch rather than M42's 1mm pitch.

So what can this lens do?

The duck picture was taken handheld at a Madison conservation park. I hadn't planned to do my first tests that way and had brought along a tripod. But when I set it up I discovered I'd left the mounting screw in my homemade close up kludge (staring in a future post). Using two rules of photographic thumb, when hand held the minimum shutter speed is equal to your focal length (750 mm equiv on my D60) and the sunny 16 rule (iso 800 to go with the lens's widest f#) it was shot at 1/1000sec at ISO 800 and f8.0.


An ok image once it is reduced for posting it is softer than I hoped when it it viewed full size.



The image quality does improve with a smaller f#. The hand held shot of the swing set was taken from my computer room window across the greenway and a 100 yards away. The noise is higher at 1600 ISO but the nuts holding the swings to the top cross bar must be no more than 1/2 inch in diameter. For a comparison the second image was taken with my 35mm "normal" lens.

Now for a few nature shots. I drove to Fish Camp Park where the Yahara river emptied into Lake Kegonsa--a spot where where swans gather. No swans when I arrived. Then as I stepped out of the car to test the lens on the local ducks, I looked up to see a flock of Mute Swans fly in. Twenty seconds of great images with the camera still locked in the trunk--if only I hadn't stopped for a muffin and coffee at PDG.

Oh well. With luck a power boat would come down the river and I could photograph them taking off. Which didn't happen. By the time the only boat I saw came by the swans had swam up river and around a bend. But I did take my share of feeding swan images. This one was taken from about 100 yards at iso 100, f16 and 125 sec using a tripod.

The other two images are of a pair that were hiding in the reeds across the river. After they decided to visit my side of the river I shot them from about 25 yards using the same settings. The image with the flapping winds is uncropped. The one of the head was cropped to remove a sidewalk in the background.

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As promised--continued

A short one. Due to some accidental keystrokes I published my last post on lens resolution while I was spell checking and otherwise editing it. Since I was still setting up my new laptop--I went with the accident and moved on to other tasks.

Eight X magnification--alas, twas but empty magnification. That means everything was bigger but there was no new detail. Even at 5X magnification I was pushing the ability of the 35mm Minolta lens to resolve detail. The finest 'hairs' on the moth's antenna were 5 pixels wide. This calculated out to be 7 microns wide or about 1/8 the diameter of the average human hair.

And if any of my hundreds of readers (humor, humor) ever want to do this at home the procedure is simple.

Use your version of my trusty machinist rule to see how big the spot you are imaging is. Convert to microns (1/1000 of a millimeter) if your part of the world never got the metric urge. Divide that number by the number of pixels in your sensor to give the micron per pixel number--1.4 in this image.

Then count the number of pixels in the tiny stuff to learn--
a--how big the fine stuff really is.
b--where your lens's resolution craps out.

And how do I know I ran up against case b? Looked at the slide with my microscope.

In an ideal world I'd now upload the microscope image. But the box of slides is buried--I suspect--under the mess of toys, books and other debris in Charlotte's bedroom/toyroom/storeroom. Time for a cleanup. But not today. The weather is too nice this weekend to waste on a cleanup.

So this post maybe continued again

Macro/micro and moth antenna

The camera club I belong to--CPM aka The Center for Photography in Madison--has moved downtown. After the last meeting in the old headquarters, I noticed that among the packing boxes there was one labeled 'Free.' Which happens to be my favorite price when it comes to photo equipment.

After checking with the club president that 'Free' really meant free, he told me "Take the whole box if you want " A strong hint since he was about to lock up. So the box and I went home.

Among the junk, and there was a lot of junk, I found a 2x neutral density filter and an Expodisk for setting a custom white balance. They will end up in my camera bag once the adapter rings I ordered from e-bay arrive. One thing I've learned about free stuff, you have to spend money to make it useful.

I also found a busted Minolta film camera with three lenses--a 28mm, 50mm and 135mm. Normally the lenses would have ended up in the busted junk pile. Minolta lenses won't mount on my Nikon and if they did they wouldn't focus properly since the sensors of the two brands aren't the same distance from the mounting flange. But since I'm now doing macro/ micro photography the 28mm lens might be an excellent find.

In an earlier post I mentioned that to closeup purist, macro photography meant your magnification went from 0.1 X (1:10) to 1X (1:1) and micro photography meant it went from 1X (1:1) to whatever magnification you could get away without using an electron scanning microscope.

{You may see the numbers in brackets on a macro lens's spec sheet. A run of the mill macro zoom should reach 1:4. Better and more expensive lens can reach 1:1. To go beyond that into the larger than life size micro mode you usually need extension tubes or other accessories.}

Until I read up on macro/micro photograph I believed the difference between macro and micro was more or less arbitrary. Even more arbitrary was the rule that the size of your bug image on the film or sensor determined whether it was life size or not. Maybe in the film age when you could hold up a slide and see the image the rule made sense. But in the digital age? My D60 sensor might be just under an inch long but I will be looking at the image on a 21 inch monitor .

But there is a bit more science behind that rule than I first thought.

In normal photography the cute girl you are photographing and the tree behind her are far larger than the image in the camera. But when as you move in closer and closer into the world of closeup and then macro photography the size difference become smaller and smaller. Finally you hit the magic 1:1 magnification where interesting things happen.

For starters your camera and your bug will never be closer. The distance between bug and sensor will be 4 times the focal length of your lens (plus or minus any fudge factor caused by principle planes). And that is where it makes major sense to flip the lens and mount it backwards.

Why? With anything except a totally symmetrical lens--identical glass on either side so the two principle planes overlap smack in the center of the lens assembly (not a very useful design)--there is always a good way and a not so good way to arrange your lens elements. While the focal length and image size might end up the same, the aberrations are different.

Anyone who has every looked at a cut out drawing of a modern camera lens's innards knows there is nothing symmetrical about them. Unless you are dealing with a specialize lens--a microscope objective for instance--lenses are always designed to image big things down on to little sensors. Once you start imaging things the opposite way the aberrations can go bad rapidly

So a reversed 28mm lens looked promising. It's 55mm filter threads screwed directly into the mount on my new bellow. For once I didn't have to spend money to use this free-be. And since the shorter the focal length of the lens the more magnification I get per mm of extension, I pulled out my trusty machinist rule to see what the lens gave me- 1/8 of an inch (3mm) visible in the viewfinder. A magnification of 8X (1:8)--now we are cooking.

But what quality of magnification? I had been using 3D flower samples, Queen Anne's Lace, because there is a field full of them behind the house. But because of the DOF and focusing accuracy problems these didn't work all that well at 4X. (See last post for details) At 8X the problems would be worse.

I needed a 2D target with precision detail. But what? In the past I'd used precision targets for testing microscope resolution limits but those babies went for big bucks. Needed to find myself a flat sample with a full range of detail

Then Charlotte came for a visit. We pulled out her new macro/micro equipment--precision optics by Mattel by way of Goodwill.

This jogged a few memory cells. Stashed away somewhere was a box of prepared microscope slides. Once found Charlotte and the dolls did their brand of science while I selected my sample-a section of a moth's antenna.

(to be continued)