Camera Lenses

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  • consoledelight 30 Oct 2013 18:18:54 141 posts
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    If anyone knows please help . . .

    Why are camera lenses always round when every way we view them are square.
    Am i missing something obvious, or are we wasting portions of an image.
  • AaronTurner 30 Oct 2013 18:23:55 7,602 posts
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    The film or sensor is normally a rectangle. The extremities of most lenses aren't good anyway.
  • Syrette 30 Oct 2013 18:23:58 43,126 posts
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    Fitting a square peg in a round hole wouldn't work.

  • smoothpete 30 Oct 2013 18:25:49 31,371 posts
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    Was this really a burning question that was eating you up inside?
  • consoledelight 30 Oct 2013 18:33:58 141 posts
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    @smoothpete

    Sadly yes. I was watching an advert for cameras and it made me wonder.
  • smoothpete 30 Oct 2013 18:46:25 31,371 posts
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    Fair enough! Old 120 film is / was square which I suppose makes the most efficient use of the lens (as opposed to rectangular 3/2 format). Also we perceive the world in widescreen so it does kinda make sense.

    Having square or rectangular camera film is much more efficient too. If we had round film, much of it would be wasted.
  • consoledelight 30 Oct 2013 19:41:19 141 posts
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    @smoothpete

    Cheers smooths.
  • AaronTurner 30 Oct 2013 19:58:56 7,602 posts
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    Oh yeah, hey no worries mate :(
  • consoledelight 30 Oct 2013 20:00:29 141 posts
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    @AaronTurner

    Sorry dude. Thanks for the info :redface:
  • AaronTurner 30 Oct 2013 20:01:14 7,602 posts
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    :-*
  • Maturin 30 Oct 2013 20:08:44 2,892 posts
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    Making square or rectangular lenses is much more complicated than circular ones. Also the best bit of the lens is in the middle, you don't necessarily want to use the edges, especially on less expensive lenses. That's why stopping down the aperture (which uses a smaller area of the lens) often results in better image quality.

    Lenses that are very good right across the frame with the aperture fully open are usually (though not always) very expensive.
  • neilka 30 Oct 2013 21:04:49 15,679 posts
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    While we're at it does anyone know why Battenberg cakes are square?
  • mal 30 Oct 2013 21:09:04 22,341 posts
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    Quite a few compact cameras (especially towards the cheaper end) have apparently rectangular front lenses. I guess they're made circular then ground down, but still, it is possible.

    I guess the reason most aren't is that lenses do rotate as they focus normally. Even if the front element doesn't rotate there are all sorts to bits of glassware in there and they all move* to enable focussing and zooming. Simplest, lightest and most reliable way to do that is to mount them in a screw thread and turn them using internal gears.

    * On interchangeable lenses at least the back element is static. That's not neccessarily true in compact cameras.

    Cubby didn't know how to turn off sigs!

  • consoledelight 30 Oct 2013 21:30:37 141 posts
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    Cheers everyone, there is some useful info here.

    I think i can consider my question truly answered.
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