Newbie & light in upper left corner.

Discussion in 'Photography Beginners' Forum' started by night_vision, Mar 22, 2007.

  1. night_vision

    night_vision TPF Noob!

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    Hello,
    I'm just starting out and getting use my Minolta Dynax 5D, could someone please explain to me why I keep getting a 'light' spot on the upper left hand corner when I try and take star trails? I cant for the life of me figure what I'm doing wrong. I've had the camera for about two years, but due to work I'm only now trying to learn all the features and photography itself.
    Any help will be greatly appreciated.

    Thanks

    night_vision

    A screen shot of the properties.
    http://databytes.org//node1/prop.png

    And the photo unedited only resized.
    [​IMG]
     
  2. xfloggingkylex

    xfloggingkylex TPF Noob!

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    is this the first picture you have experienced the light in the corner? Does it happen on all your long exposures?
     
  3. shorty6049

    shorty6049 TPF Noob!

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    that happens when a charge builds up on the sensor. Its pretty common with long exposures like star trails. I cant remember the exact term for it, but its something that you just have to deal with in long exposure astrophotography...
     
  4. shorty6049

    shorty6049 TPF Noob!

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    I just looked around, and i THINK its called thermal noise... if you can keep the sensor really cool, you will have less of it, but i'm going to keep looking around for other answers, i've experienced it on more than one occasion though as well when photographing star trails
     
  5. shorty6049

    shorty6049 TPF Noob!

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    I posted a question on the cloudynights astronomy forums so i'll get back to you with a fuller answer when someone answers my thread, unless someone else on here knows this answer off hand.
    from what i have been able to tell, it MIGHT be called charge leakage...
     
  6. shorty6049

    shorty6049 TPF Noob!

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  7. night_vision

    night_vision TPF Noob!

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    Looking through the rest of my photos that I took last night with an exposure of a minute or longer including the one above all seem to have it to some extent or another.

    shorty6049
    Thanks I'll keeps tabs on the progress.

    Thanks for the quick replys.

    night_vision
     
  8. Garbz

    Garbz No longer a newbie, moving up!

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    hey night_vision. I also have this problem on the Nikon D200. It is unfortunately common to all cameras although some less than others. I took a 2 hour exposure on the D200 and the sensor gets HOT. The entire image was purple. My long exposure noise reduction takes care of it. However since you have already taken the image I suggest hit up the EXIF data for the exact exposure time. And take another image of the same length with the lenscap ON. In photoshop then add the second layer over the first as a difference layer. This will subtract the purple fringing from the rest of the photo.
     
  9. Digital Matt

    Digital Matt alter ego: Analog Matt

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    Try shooting film and this won't happen. Digital sensors are not yet capable of managing very long exposures without the effect of burnt pixels, and noise. A good slide film will work wonders for star trails.
     
  10. night_vision

    night_vision TPF Noob!

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    Hey Garbz,
    Is that a camera setting or something done in photoshop?


    Digital Matt,
    Unfortunately I don't own a film camera, but thanks for the tip.
     
  11. Digital Matt

    Digital Matt alter ego: Analog Matt

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    You can probably buy a Minolta 35mm slr for under $100 used.
     
  12. shorty6049

    shorty6049 TPF Noob!

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    thats one reason dedicated astrophotography ccd cameras have a giant heat sink on the back, the goal is to take heat away from the sensor as quick as you can to minimize the effect of that purple cloud that always seems to roll in...
     

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