Question about odd background patterns

Discussion in 'Sports' started by david_klaffenbach, May 19, 2016.

  1. I shot this the other day:
    [​IMG]
    I was struck by the appearance of some of the out-of-focus highlights, such as seen in this crop from the upper left corner:
    [​IMG]
    I've since found similar patterns in photos by other folks online (and it happened to be in daytime baseball shots), so I don't think it is due to a lens defect particular to my lens.
    I'm just curious if anyone knows what the explanation is for this kind of background pattern. The lens is a Tamron 300mm f/2.8, shot at f/4.
     
  2. Could be flare from the stadium lights or glare from someone wearing something shiny.

    It is either that, tiny UFOs or manifestations of photon impact damage in your lens :)
     
  3. Hi Ellis, I'm fairly certain it starts as a specular highlight off of glasses, an aluminum beer bottle or something else shiny. It's an afternoon shot, so it's sunshine at work. What I'm not sure about is why it isn't a smooth circular pattern (which is what I get if I try to make this happen with out-of-focus streetlamps or such).
    The lens is old but new to me, and it has more internal dust than any of my other lenses, but I don't think that's the cause of this and the lens appears to be working well in general. It was once a rental lens, so I'm sure it's had its share of photon impact damage (which by the way is a real thing if you're dealing with high intensity lasers - they call it optically induced damage!).
     
    beegeedee likes this.
  4. If it is a reflection it likely isn't perfectly round as the object is neither a light source or perfectly smooth.
     
  5. I would guess that its someone taking a photo with the flash enabled.
     
  6. Speckle: https://en.wikipedia.org/wiki/Speckle_pattern
    While normally it comes from laser sources, at long enough distances (far field) it can happen from small bright point (or close enough) sources. Easiest to see with bright street lights at a distance. If you wear glasses, take them off outside and look at a far away street light.
    It comes from the combination of diffraction and interference.
    Not understanding diffraction is the reason why early astronomers, such as Galileo, didn't realize how far away stars were. They come out as circles in telescopes, such that they look closer than they are.
     
    beegeedee likes this.

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