Astigmatism and other vision defects

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colohank
Posts: 113
Joined: Sat Jul 24, 2021 6:07 pm
Location: Fruita, Colorado, USA

Astigmatism and other vision defects

Post by colohank »

Interference figures in my progressive-lens eyeglasses revealed by cross-polarization. This image is inverted. The glasses were resting on a reflective sheet of black acrylic, and they were illuminated from the rear by the LED display from a repurposed digital picture frame. The light from the display is inherently polar. I rotated a polarizing filter mounted on the camera lens to achieve extinction of the light from the digital picture frame except, of course, where it passed first through the plastic eyeglass lenses. Thus, the interference figures. Other distortions around the lens perimeters are caused by pinching of the eyeglass frames. For whatever reason, the acrylic sheet on which the glasses were resting renders as gray. Focus of this image was by gosh and by golly, since I couldn't wear my glasses to manually focus. Nikon D810, 105mm f/2.8 Micro-Nikkor fitted with an older Nikon linear (not circular) polarizing filter. ISO 400, f/16, 0.8 second.
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