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Simple photomicrography stand for DSLR cameras

Last Updated: 9th Dec 2010

By Henry Barwood

Construction of a photomicrographic stand for DSLR cameras

Most micromineral collectors use a dedicated microscope to photograph minerals. These can consist of a binocular scope with one eyepiece dedicated to a digital camera, or a trinocular microscope with an attached phototube. Configurations can range from simplistic to extremely complex (high end) units. In general imaging through a microscope suffers from several problems.

Focusing is often difficult, and absent a live-view function on the digital camera, nearly impossible. Most digital cameras, including DSLR, either have live-view, or can be connected through a video device for assessing the level of focus. Many cameras now have software that can control all the camera functions directly through a computer and also contain routines for focusing. Most of this software comes from the astrophotography sector of digital imaging.

A far more serious problem, notably with DSLR cameras, is shutter shake caused by the “slap” of the viewing mirror retracting. These vibrations can seriously degrade an image, particularly those taken at high magnification. Many photographers will use various schemes to minimize vibrations such as mirror lock-up (not available on most DSLR cameras) and delayed triggering of the shutter.

Recently, I grew frustrated with vibration blurring on my images taken with a Nikon SMZ-10 trinocular microscope. This venerable workhorse, when fitted with a Nikon UFX shutter, will produce very high quality film images, however, when used with an SLR, digital or otherwise, it suffers from considerable camera shake. The phototube is quite long and the microscope stand is not particularly heavy. When my Nikon D90 is mounted, I can take reasonably high quality images up to around 15X. Beyond that there is degradation of the image.

In order to mitigate this problem, I decided to build a stand for a system I first used for photomicrography. Most high end micromineral photographs are taken with a bellows or extension tube set-up that utilizes direct projection from lenses that are normally used on specialized macro cameras. Note that these are not the same as multi-element lenses that shift the front elements to achieve close up images, nor are the normal camera lenses that are reversed for close-up work. The least expensive lenses for photomicrography are enlarging lenses.

Enlarging lenses are relatively simple lenses, but they are highly corrected, have a diaphragm and do not suffer from loss of image saturation. I adapt standard M39 enlarging lenses to Nikon using cheap adapters available from China. My favorites are Nikkor enlarging lenses.

The stand was constructed of wood, and is a simple flat base with a vertical holder for extension tubes (figure 1, 2 and 3). Clamps for the tubes were made by drilling and splitting pieces of wood so that they grasp the tubes tightly (silicone rubber was used to seat the tubes and hold them snugly). I strung together 6 sets of extension tubes, such as those that are obtained from China for only few dollars each set. To focus, the base has a machinists micrometer stage mounted as a stage. Such units can be had cheaply off the internet, but any X-Y or X-Y-Z stage can be adapted (figure 4).

When finished, the tube set is firmly clamped into the holder. Accessories such as a half tennis ball rotating stage allow the specimen to be positioned accurately. This stage is good up to around 90X magnification without noticible image degradation.



This is a test photo taken of some very tiny crystalsof labuntsovite and ancylite from Jones Mill Quarry (<0.1mm). Using a microscope, no details at all would be visible in the image.



After using the stand with the D90, I added a Zeiss electronic shutter from my spare parts box to determine if the low noise shutter would improve the image quality. The first image is taken with the D90 shutter:



The second image was taken with the Zeiss electronic shutter:



The differences at this extreme enlargement are subtle, but the resolution with the low noise shutter is clearly better.




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Comments

Thanks for the information and pictures. I had been reading about extension tubes and keep hearing that connecting them end to end will cause image artifacts. I am not sure they are obvious here.

Robert Simonoff
20th Dec 2010 4:58am
Actually, I forgot to mention that I had cut light baffles for the interiors of the tubes. You are correct that the unmodified tubes will have reflections from the dark, but polished metal surfaces. These tend to form either a central "hot-spot" or annular rings on the images. With all the things that are happening for our Christmas, I haven't had time to play with the unit and make needed adjustments. Thanks for your interest.

Henry

Henry Barwood
25th Dec 2010 1:50am
Thank you for your efforts and documentation of them. I am very interested in microphotography and am, as of now, still not happy with my own results. I am always interested in ideas that will move me forward. Ideas, that is, costing less than 15,000 USD!

Bob

Robert Simonoff
27th Dec 2010 11:29pm
$15,000? I shop at eBay and LabX, and rarely spend more than $50 on an item. The trick is to seek out older stuff that can be modified to modern techniques.

My first images were taken with an old war-surplus Speed Graphic 4X5 camera. I replaced the lensboard with an old Kodak 50mm anastigmat mounted in a shutter. My film holder was another old scrap Kodak 35mm camera literally glued to a 4X5 inch board that slid into the back of the Speed Graphic. To focus, I used another board with a tube cut to the length of the camera/board unit, and a piece of ground glass. It worked fine and I used it for several years (I was a teen at the time and had no money at all!). Depending on the bellows extension, I got between 15-25X magnification.

Henry

Henry Barwood
28th Dec 2010 1:50am

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