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Mineral Photographyusing immersion to photograph inclusions in rough crystals

25th Sep 2015 19:10 UTCDennis McCoy

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I purchased a USB microscope last week, and have been having fun experimenting. While trying to look at some inclusions in amethyst chips and slices yesterday, I decided to try immersing the crystal in water to smooth rough surfaces and eliminate (at least partially) the reflections from contact faces. It worked like a charm. My initial attempt was marred by the reflection of the lighting LEDs and vibration waves on the water surface. My solution to this was to bring the housing below the water surface. This allowed me to focus on an area inside the light ring reflection and eliminated tiny waves in the image area.


this first one is a simple stack of 2 photos



in this one you can see some small bubbles held by surface tension. Each one reflects a tiny image of the light ring.
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25th Sep 2015 19:49 UTCDennis McCoy

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The set up.

25th Sep 2015 20:35 UTCOwen Melfyn Lewis

What's your approx horizontal field of view in the second shot, Dennis?


A couple of things you might like to try:

- Use isopropyl alcohol rather than water as your immersion fluid. Higher refractive index and will eliminate/much reduce bubble formation and reduce unwanted reflections more than does water.

- Replace your china pot with a cut-down dixie cup. Place the dixie cup on a small low voltage light table (cost about 20-25 bucks) use that as your main light. In general, transmitted/side-lighting works best for illuminating inclusions in crystals. The translucent white of the thin dixie cup improves the diffusion of the light from your light table (that should already be fitted with a partially effective diffusing screen).

- Work on critically sharp focusing and also try increasing the number of shots in your stacks.

26th Sep 2015 01:53 UTCDennis McCoy

Thanks for the tip, Owen. I will have to find some other way of holding and adjusting the microscope. The stand it came with is too sloppy to get accurate stages.

26th Sep 2015 03:49 UTCJames Pool

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If you have a regular microscope that has screw holes for attaching things like ring lights, you can try using a metal broom holder clip and attach the usb microscope that way. It should also work for any screw holes that are on the stage. This allows you to use the much larger and stable microscope stage for finer controls. I did have to use a shim to get the broom clip to fit snugly to the screw holes on the microscope stage and to allow enough clearance for the vertical alignment of the usb microscope. As you can see from the photo, this setup would work better with a boom type microscope stand as I have to use an external platform as the base of my microscope does not reach far enough for example placement.


You may have to adjust the curve of the broom clip to assure of a secure firm grip of the usb microscope. A standard hardware store should carry these clips. Lacking thread holes you could either glue a correctly sided nut with a shim for proper fit or a temporary setup with shims and rubber bands or plastic tie clips.

27th Sep 2015 04:18 UTCDennis McCoy

Owen, sorry I missed your question about the field of view. Horizontal FOV is approx. 2 cm.

27th Sep 2015 08:30 UTCOwen Melfyn Lewis

So magnification is quite low, about x10? At that sort of mag level, if you have a camera that has a macro mode and use that rather than the USB microscope, you might find it easier to adjust your lighting and also to get sharper images. However, you would also need a camera that allows manual focusing, otherwise all your inclusions will be out of focus as, in auto-focus mode, a camera will always focus on the surface of the specimen nearest the camera.


Working with a camera and with some cropping of the image file, I find I can make decent images that have about a 1 cm FOV.
 
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