Archived posting to the Leica Users Group, 2011/09/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Here is an interesting visual problem that I figured out abut a year ago. The explanation will have meaning to photographers. A year or more ago I noticed a strange double vision in my right eye. It varied in extent from day to day, but looking at a vertical post, e.g. the post of a street light, I would see a faint ghost image displaced slightly to the right. The ophthalmologist had no explanation. Ultimately, I noticed a very interesting effect when looking at traffic lights from about a block away. A green light expanded into a triangle of the light and two ghost images below it. A red light was only barely affected. Hah, wave-length dependent; has to be refraction. A lot of thought as to what the hell could it be, and suddenly I had an aha moment. As you age, the gel in the eye withdraws from the retina. It had to be a tiny bit of the gel that stuck to the retina. Think about the micro-prisms that are the focusing aid on the screen of an SLR. I confirmed this with my glasses. I wear trifocals. If I shifted my glasses so that I was looking at the traffic light through the mid-distance portion, the size of the triangle increased. My ophthalmologist was amazed. Herb -- Herbert Kanner kanner at acm.org 650-326-8204 Do not meddle in the affairs of cats, for they are subtle and will pee on your computer!