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Photomicrography

Last Updated: 31st Aug 2008

By Pascal Chollet

Hello. I'm gonna tell you about my (small) experience in close up and photomicrography.

I collect micromounts since I was a teenager and the main problem with this kind of collection is to share it with other persons. especially with people who are not wise with mineralogy and can't stand to look through a binocular for a long time. I'm also afraid to show my favourite cyanotrichite for example and see someone put his fingers on it !!!

So I decided to try to take pictures of my best ones...

It is often said that good pictures can't be taken through binoculars but with specific photographic material. I've never tried to take pictures through a binocular anyway and I won't say nothing about a subject that I don't practice.


I started with a 35mm single lens reflex (SLR) - Rolleiflex SL 35 and some extension rings, a pretty good material to take usual pictures but it quickly showed limitations for close up photography. And I needed a bellow - rolleiflex bellows are really hard to find and novoflex bellows are short and expensive.

after some investigations I found a nikon PB-4 bellows and decided to migrate to Nikon material. there were different reasons for choosing Nikon rather than other cameras. here are the main ones :

- Nikon provides lots of different materials, and very specialised ones you can hardly find to others manufacturers. the PB-4 bellows is quite the only one made for 35 mm camera that offers tilt and shift possibilities. Mamiya also built one but it's very hard to find and it only fits discontinued mamiya cameras.

- Nikon never changed the F mount : this means that you can use a old lens from the sixties on a brand new digital SLR. you can also use an autofocus lens on an old camera body - all this with just sometimes metering limitations. there are now some stronger restrictions with the G type lenses who does not have any aperture rings and can't be stopped down on mechanical bodies, but they still can be mounted.

- Nikon provides very strong material and the ones of the "pro" line are quite indestructible. I've read about a F5 camera that have been dropped off the bag and has rolled for about 50 m on solid rock in french montains last year and was still working properly. only the filter ring of the lens had serious damages. I won't try this kind of crash test with my material anyway.

So I purchased an used Nikon F3 body. a very good material. I also purchased the type E focusing screen for easyer focus. Next I had the luck to find and purchase a high maghification DW-4 wiewfinder.

Next problem was the choice of lens. I was working with a 55mm micro nikkor wich allows to reach the magnification ratio of 1/2 by itself. the use of extension ring and bellows increases the magnification possibilities. I built by myself an inversion ring to be able to use the lens in reversed position. so the distance between lens and object is always large enough for easy illumination, and the image is sharper than in normal position when the magnification is more than x1.

With this material I was able to reach x5 magnification. but I wanted to go further. There are 2 ways to do it : increase the mechanical camera lengt and/or use shorter focal lenght. I've tried several lenses without succes. wide angle lenses are very poor microphotography lenses. I had to find a dedicated lens. Quite all the manufacturers built some but they're all discontinued and hard to find : the most famous ones are the zeiss luminar, Leitz photar and Nikon macro-nikkor (wich are also the more expensives ones. don't make confusion with the micro-nikkors that are ordinary lenses with close-up possibilities).

Other common microphotography lenses are made by canon, olympus, minolta, etc... these ones are cheaper but the quality is not the same, althought olympus & minolta are very good ones. Minolta (and leitz with the Photar) made the shorter focal lenght microphotography lens ever made : 12,5 mm. Minolta and Leitz have been working together to create minolta microphotography lenses and their optical formulas seems to be quite the same as photar lenses. but minolta mechanical building is cheaper.

there exist several dozens of different microphotography lenses but most of them are very rares. All theses lenses are treaded with the RMS (= Royal Mount Screw) standard screw of microscope objectives. so I also had to find or build a "F mount RMS" adaptator ring. I took a damaged adaptable lens and picked the baionet to build the adaptator.

So, I found a canon 20mm microphotographic lens. the main problem with this one is that diffraction appears as soon as you try to close the iris. not a very good lens anyway.

I've found other problems with microphotography :

- first : light metering. NEVER trust the metering cell of your TTL camera body. even with the "red blue green 1003 segments" of the Nikon F5 and Nikon D1, D2 and D3 series metering can be wrong. I took pictures on Dia, bracketting by full IL, had the film treated and looked at the result. so I did again the same photography with 1/3 IL bracketting. I had to write all the photo parameters to take the second shoot with the same conditions. I had to be very carefull with everything as my first attempts were done with vivitar 285 non-ttl electronic flashes unit. so I had to note also the flash distance and power of the unit .

It learned me how to be very concienscious and take care about everything.

I now use a fiber optic with correction filter to get a 5500° K color temperature and illumination is pretty much easyer than the use of flashes.

- Second problem is the vibrations - all your system must be very rigid. The softer vibration will destroy your image, especially if you work at a high magnification ratio.

- third problem is the depth of field. you can stop down to increase it but diffraction will soon appears and kill your image. the photo of capgaronnite posted on mindat with a magnification of x35 was took a full aperture. as soon as I tried to stop down, the diffraction blured the picture. When I shoot with digital camera I take a picture at every available aperture. So I can choose the best one where depth of field is the greater before diffraction gets too strong and destroys image definition. It now guides me to take analogic pictures, althought argentic films are less sensitive to diffraction than digital captors. This fact is a result of the structure of the digital target. It is known that even in "ordinary" digital photography diffraction becomes a problem when stopping down more than f/11 and actually it is the limit with my lenses and the Nikon D1x dSLr, even if the Micro-nikkor can be stopped down up to f/32



I now work with a Nikon D1x digital camera but still use the Nikon F3 to get dias for the best pieces. the quality of a dia on a 2 meters screen is really better than digital picture. I also leaved the 20 mm canon as I found 2 zeiss luminar lenses (25mm - the most useful - and 16mm for high magnification) and I use a nikon vintage stand. I also purchased a second bellows to get a longer mechanical camera lengt for high magnification. I use also different little things, especially a "clamp" laboratory plate so I can easily move up and donw the object instead of moving all the photographic system, where both bellows and camera body are fixed on the column, to avoid vibrations. on this plate is fixed a X-Y stage coming from a Zeiss microscope. centering the object is really easyer with this appliance than moving it with fingers.


Here's a wiew of the material :

Larger Version using width setting


The Nikon F3 body with DW-4 wiewfinder is mounted on the PB-4 bellows. 25mm Zeiss luminar is mounted on the front plate of the bellows. 16 mm luminar lens is on the laboratory plate, partially hidden by the gooseneck of the optic fiber illuminator. You can see the second bellows with the 55 mm micro nikkor mounted.

Pascal



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EDIT : aug 31, 2008

Hello

it's about the improvements done to my system.

I began to use combine ZM few months ago and so I needed a micrometric adjustement stage. I first used a Zeiss vintage microscope, placing the box with the mineral on the tube. but this microscope is a collection item in mint condition and I was afraid to do some damages (there's always some sand and dust around).

So I purchased an old microscope on a secondhand market. an ugly piece for parts, with no eyepiece and no objectives. but it has a X-Y stage plus Z micrometric movement under the stage. exactly what I needed.

I also had the luck to find for few euros a 150w polymerising halogen light source with a long optic fiber. so I cutted the tube arm of the microscope and had the head of the optic fiber fixed on the bottom part. the head can slide horizontally on the arm and the height adjustement of the light source is easily done with the rotating knob.

I finally picked the nosepiece of the microscope and had it firmly fixed on a nikon F extension tube. so my three luminar lenses are mounted together on the bellows, exactly as microscope objectives. more than easily switching between lenses, centering the specimen is also easyer and faster. I use the 63mm lens and it's lows magnification to focus on what I want to picture in the middle of the wiewfinder and then switch on another lens for higher magnification. the nosepiece can hold 4 objective so there is a free hole for the 40 mm luminar lens I'm still looking for at reasonnable price. (I already own 16, 25 & 63mm)

as a picture sometimes tells more than a long speech, here's what the system looks like :



Larger Version using width setting


Pascal




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