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41313Re: spherical mirror

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  • Erik Krause
    May 2, 2010
      Am 02.05.2010 21:12, schrieb _kfj:
      > But: it costs a lot of money and/or has chromatic aberration (at
      > least on the edges).

      Wrong. A Samyang, a Zenitar or a Peleng are relatively cheap. The
      Samyang is very good:

      > So I was wondering about spherical mirrors. They
      > ought to be able to produce images of almost the whole field of view

      ... except what's behind the camera and what's behind the mirror. In
      practice the distortion near the mirrors edge is so high you won't get
      usable image data there. Hence the vertical FoV is limited to about 120°
      to 160°.

      > and have no CA,

      The mirrors not, but you still need a lens to shoot them, which still
      might have CA. Mirrors have other drawbacks: They don't reflect 100% of
      the ligth, any dust speck or finger print will be visible in the image,
      hence the dynamic range is limited. In short: nothing for serious work.

      > be lightweight and potentially even cheap! Has anyone
      > out there used one (or is there a ready-made spherical-mirror-lens
      > around)? And where could one find optical grade spherical mirrors if
      > there are no ready-made lenses?

      In addition to what Uri wrote: You can order single spherical lenses
      f.e. from http://www.linos.com and let them coat it. I asked some years
      agon and if I remember correctly the price was below 100 euros.

      > How does one go about getting the
      > view and not an image of oneself when using a spherical mirror? Maybe
      > there are alternatives which aren't spherical but some other convex,
      > maybe pointed, shape?

      Either you cut the camera out later or need to shoot from two different
      directions and stitch the result.

      Some years ago Uwe "hammernocker" Roßberg made a mirror for himself and
      shot some panoramas: http://www.hammernocker.de/panorama.php (choose a
      category on the left side).

      You'll probably agree that this is mainly for fun and not for serious
      panorama work...

      Erik Krause
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