Friday, March 23, 2012

Thurs-Demo: The Next One Posted on Friday Because I Was Busy Thursday

This isn't a trend, but I seem to be rather busy on Thursdays. So much so that yesterday's demo didn't happen. Perhaps I'll describe what I was up to at some later point.

Today, however, I took advantage of the light output from an iPad. Many computing devices that have an LCD type screen emit polarized light. It's why I rarely wear sunglasses when I'm out taking pictures - the polarized glasses cut out too much - sometimes all - of the light from the review screen on the back. Wearing polarized sunglasses and looking at a computer can also be tricky.

But stick the iPad behind a transparent, isotropic material and then slap a polarized filter in front of the camera and you have an instant stress-field viewer. I redid the shot of a small cap gun charge through gelatin, but this time the only light was coming from an iPad.

This turned out much better than I had hoped. First, I didn't have a lot of light to work with. Second, many computer screens will produce scan lines because the screen is "refreshing" at some frequency (it's why video of older phosphor screen monitors "flicker"). But the iPad sent out a nice steady light (I made a blank white slide in keynote and just had that as the display).

Now I think I need to get my hands on some of those old fashioned 4"x4" rock thin sections and try photographing them...

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