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Thread: Effect of Star filter without star filter

  1. #1

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    Effect of Star filter without star filter

    Effect of Star filter without star filter

    I took this photo in Paris late May. I did not use any star filter but there was kind of star filter effect.

    I wonder why it could happen.

    C&C is also appreciated

    Exposure: 20
    Aperture: f/22.0
    Focal Length: 20 mm
    Exposure Bias: -1 EV
    ISO Speed: 100

  2. #2
    flipmode's Avatar
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    Re: Effect of Star filter without star filter

    I'm not 100% sure but I think it's because of the small aperture you're using (f/22), similar to when you want to get a starburst effect. Someone correct me if I'm incorrect.

  3. #3

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    Re: Effect of Star filter without star filter

    Quote Originally Posted by flipmode View Post
    I'm not 100% sure but I think it's because of the small aperture you're using (f/22), similar to when you want to get a starburst effect. Someone correct me if I'm incorrect.
    Spot-on Chris

    Effect of Star filter without star filter

  4. #4

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    Re: Effect of Star filter without star filter

    I did google search and found similiar explanation as yours. Thank you very much! It is interesting to know.

  5. #5
    pwnage101's Avatar
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    Re: Effect of Star filter without star filter

    Why are there more blades in the sunstar in colin's image that those of yjiang's? Surely the aperture doesn't have 14 blades.... isn't 6-8 blades the norm?

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    Re: Effect of Star filter without star filter

    Quote Originally Posted by pwnage101 View Post
    Why are there more blades in the sunstar in colin's image that those of yjiang's? Surely the aperture doesn't have 14 blades.... isn't 6-8 blades the norm?
    Good question Troy - my answer to which is "I don't have a clue"

  7. #7
    pwnage101's Avatar
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    Re: Effect of Star filter without star filter

    welcome to the club

  8. #8
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    the reason for the number of star points.

    Folks describing interference at edge of aperture are right, Light spreads out (diffracts) perpendicular to the edges of the blades, with star spikes at right angles to flat/straight edges of the aperture opening.

    So (if you really care) a 5-blade iris will give a 10-point sun star, a symmetical 6 blade iris a 6-point star (because opposite edges are parallel, their points overlap), 7-blade iris a 14-point star, etc...And this effect may be less pronounced/more diffuse with rounded iris touted on some newer lenses
    http://photo.net/medium-format-photography-forum/001uPA

  9. #9

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    Re: the reason for the number of star points.

    Effect of Star filter without star filter

    This was at f29

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