HELP! Noise caused by refraction?

Lenny53 Jan 14, 2006

  1. Lenny53

    Lenny53 TrainBoard Member

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    Any ideas about this, happened on 4 trains in my last 2 outings?

    [​IMG]
     
  2. MK

    MK TrainBoard Member

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    The problem is the headlights are hitting your lens just at the right angle to cause flare. It's similar to taking pictures into the sun.

    Can you stand more off angle? The more direct you are the more this problem rears its head.
     
  3. Gats

    Gats TrainBoard Member

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    People buy star filters to recreate the same effect! I reckon it looks great! [​IMG]

    Or are you talking of the green spots that look like the headlight/ditchlight arrangement upside down and to the left?
     
  4. Lenny53

    Lenny53 TrainBoard Member

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    I never encounter this problem using the same AF lenses shooting film so I do not understand why this happens when using digital.
     
  5. Lenny53

    Lenny53 TrainBoard Member

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    It is the green spots I'm talking about.
     
  6. MK

    MK TrainBoard Member

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    Digital has far more of a problem with flare due to the much more shiny reflective surface of the CCD. A lot of manufacturers are coming out with "digital" lenses and one of the design criteria is to get the light rays to be perpendicular to the sensor when it hits.

    "Film" lenses have the rays hitting the sensor in an angle. There's nothing wrong with that but in severe cases like yours it does increase flare.

    If you really can't avoid it, how about Photoshop?
     
  7. Lenny53

    Lenny53 TrainBoard Member

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    This is bumming me out somewhat, I never had any issues like this shooting head on with film.
     
  8. BoxcabE50

    BoxcabE50 HOn30 & N Scales Staff Member TrainBoard Supporter

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    Hope you can figure this out. Digital is so much different from my old SLR. Am struggling to learn all the tricks. A lot of bells and whistles to assimilate...

    [​IMG]

    Boxcab E50
     
  9. Lenny53

    Lenny53 TrainBoard Member

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    Yes Sir! Quite the learning curve ahead.
     
  10. Pete Nolan

    Pete Nolan March 17, 2024 TrainBoard Supporter In Memoriam

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    Lenny,

    I just don't know! The green spots look like internal lens reflections, at least at this resolution. The two top ones are oriented at the same angle from the lights; I don't know about the third one at the bottom, or the bright spot on the rails below that.

    What was the camera, lens, and f/stop?

    If you want to send me a larger image, I'll be happy to look at it.
     
  11. Lenny53

    Lenny53 TrainBoard Member

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    Hi Pete;

    The top 2 spots are from the ditch lights, the bottom one from the headlight. Shot was taken with a Nikon D50 and a Sigma 70-300mm APO D AF zoom. I got this repsonse from DWIG on the Nikonians board;

    "Three green spots that are almost certainly reflections off of the sensor, actuall the filter in front of the sensor, bouncing back after reflecting off of the rear element of the lens, a common occurance with digital cameras and usually is inverted 180 degrees about the center of the image from the light source that produced it, the three headlights in this instance."

    Check your inbox.

    Cheers,
    Lenny
     
  12. chessie

    chessie TrainBoard Supporter

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    I have seen those green spots in pictures I have taken with my new lens... I had chalked it up to the light reflecting caused by the UV filter. I never had that issue with my old lens, but I didn't have a filter on it!

    Harold
     
  13. chessie

    chessie TrainBoard Supporter

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    Here's a shot that I found has a green spot:
    [​IMG]

    (look below the cab)

    Harold
     
  14. chessie

    chessie TrainBoard Supporter

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    I find it more likely to occur when shooting nearly head on in lower light...

    If I get one that is offensive, I usually just edit it out.

    Harold
     
  15. Lenny53

    Lenny53 TrainBoard Member

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    I will test without a filter although the filter never posed a problem when shooting 35MM film.
     
  16. Lenny53

    Lenny53 TrainBoard Member

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    Interesting, only a single spot. The problem seems to occur when the source of light is near the center of the frame.
     
  17. MK

    MK TrainBoard Member

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    It's not the filter in front of your lens. The light is bouncing around inside the lightbox of your camera and causing flare internally.

    There are a lot more shiny surfaces inside the lightbox of a DSLR than a SLR.
     
  18. Lenny53

    Lenny53 TrainBoard Member

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    That's what I would think given my experience with filter use and shooting 35mm film. However, the jury is still out given post #7 on this thread.

    http://www.nikonians.org/dcforum/DCForumID201/15281.html
     
  19. Pete Nolan

    Pete Nolan March 17, 2024 TrainBoard Supporter In Memoriam

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    Lenny sent me a larger image, and I tend to agree that it is flare caused when light reflects off the filter in front of the sensor (not the filter in front of the lens), and then reflects back off the rear of the lens. At first I had trouble with the location of the bottom spot; then I realized, before I returned to this thread, that the three spots formed a triangle of the same geometry, only inverted. As a camera records images "upside down"(top is bottom, left is right), it makes sense that this is a reflection off the back of the lens. The recording (i.e. emulsion) side of film is not shiny.
     
  20. Lenny53

    Lenny53 TrainBoard Member

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    I tested removing the external UV filter in a couple of different light conditions and saw the spots in the finder, which I had noticed previously, however none appeared to be captured on any of the images. A little unsettling going without anything protecting the front element of the lens but the results speak for themselves.

    [​IMG]
     

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