chipdatajeffb
Xpolar setup
My new setup for making macro-scale (~1:2) images of meteorite thin sections in cross-polarized (Xpolar) light.
This is much less expensive and easier to use than a petrographic microscope, which doesn't give you a complete view of the thin section in any case. So, for macro views this is a much better approach.
You can still find used Bowens Illumitrans slide copiers for under $100. For this purpose, all you need to work is the bellows, the camera adapter, an enlarging lens, and the substage strobe and focusing lamp.
You could do this with any light table (tracing box) as well.
The only addition is two linear polarizing camera filters (the two pictured here are Hoya filters in 67mm size, but any size over 48mm will work).
The method is simple:
1. You illuminate the section from below, by putting it on top of one of the polarizers.
2. Focus the camera (a film camera is standing in here for my DSLR, which was busy taking its picture) -- a viewfinder magnifier helps a lot here.
3. Place the second polarizer over the thin section, rotating the upper polarizer relative to the lower one until the field goes dark (only the section will be illuminated).
4. Flash the strobe to make the image. Depending on the magnification in the setup, the f-stop setting of the copier lens, and the darkness of the slide, multiple flashes may be needed.
Total cost of this setup is just under $120 (used pieces) not counting the camera, about 1/3rd the cost of an entry-level petrographic microscope. If you use a simple tracing box for illumination (which will require a time exposure on the camera), you can do it for about half that.
Note: Circular polarizers (the most common type used with cameras) don't work as well, because they don't completely cross-polarize. Be sure to specify PL, not CPL, filters if you go shopping.
A tip of the cap to the late Lawrence A. Chitwood for the method used here.
Some early results:
www.flickr.com/photos/chipdatajeffb/2704234942/
www.flickr.com/photos/chipdatajeffb/2712042682/
Xpolar setup
My new setup for making macro-scale (~1:2) images of meteorite thin sections in cross-polarized (Xpolar) light.
This is much less expensive and easier to use than a petrographic microscope, which doesn't give you a complete view of the thin section in any case. So, for macro views this is a much better approach.
You can still find used Bowens Illumitrans slide copiers for under $100. For this purpose, all you need to work is the bellows, the camera adapter, an enlarging lens, and the substage strobe and focusing lamp.
You could do this with any light table (tracing box) as well.
The only addition is two linear polarizing camera filters (the two pictured here are Hoya filters in 67mm size, but any size over 48mm will work).
The method is simple:
1. You illuminate the section from below, by putting it on top of one of the polarizers.
2. Focus the camera (a film camera is standing in here for my DSLR, which was busy taking its picture) -- a viewfinder magnifier helps a lot here.
3. Place the second polarizer over the thin section, rotating the upper polarizer relative to the lower one until the field goes dark (only the section will be illuminated).
4. Flash the strobe to make the image. Depending on the magnification in the setup, the f-stop setting of the copier lens, and the darkness of the slide, multiple flashes may be needed.
Total cost of this setup is just under $120 (used pieces) not counting the camera, about 1/3rd the cost of an entry-level petrographic microscope. If you use a simple tracing box for illumination (which will require a time exposure on the camera), you can do it for about half that.
Note: Circular polarizers (the most common type used with cameras) don't work as well, because they don't completely cross-polarize. Be sure to specify PL, not CPL, filters if you go shopping.
A tip of the cap to the late Lawrence A. Chitwood for the method used here.
Some early results:
www.flickr.com/photos/chipdatajeffb/2704234942/
www.flickr.com/photos/chipdatajeffb/2712042682/