A&P photoshop question

Discussion in 'Lifestyle' started by ericande, Jan 18, 2009.

  1. ericande

    ericande Active Member

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    I took a series of photos tonight for a star trail shot over downtown Seattle but since the city lights are so bright the stars are somewhat dark. Once I separate the sky from the city, what is the best way to brighten the stars? If I just use levels it brightens the sky too which I don't want. Boosting the contrast brightens some stars and makes others disappear. Basically what I want to do is only brighten parts over a certain level (the stars) and leave the almost black sky completely alone. Any easy way?
     
  2. johan

    johan Active Member

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    Location:
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    curves
     
  3. EWhytsell

    EWhytsell New Member

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    I'm guessing you used a tripod and that you also combined the images to get the trails. Post an example.

    What you probably need to do will involve very small movements of curves then levels. Use curves to protect the highlights and set a very subtle C-curve in the middle each time. Then use levels to bring the highlights back up and also drag the mid tones down to 1.2 each time.

    Do this around 6 times and then set your black point where your happy with the sky color and you could be good to go.
     
  4. percent

    percent deluded

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    Also...you could use the dodge tool to individually brighten stars.
     
  5. ericande

    ericande Active Member

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    Here's the picture. I know the city is blurry, I'm fixing that later. You can click on it for full-size.

    I think next time I try this I just need to do shorter exposures and a slightly larger aperture to bring out the stars and minimize the city lights.


    [​IMG]
     
    Last edited: Jan 18, 2009
  6. percent

    percent deluded

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    good luck.

    The stars aren't coming out because they are just too weak compared to the city lights. There is a lack on contrast between the sky and the stars. "Natural" methods like levels or curves wont save you here. I'd say your only hope would be artificially brightening the stars - either with a brush or dodge tool.

    I was thinking the stars would be mostly dots.
     
  7. EWhytsell

    EWhytsell New Member

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    Link to larger one not working for me.
     
  8. EWhytsell

    EWhytsell New Member

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    Here's what I was able to do with the small version. With the RAW files you could probably make this into something usable.

    [​IMG]
     
  9. ericande

    ericande Active Member

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    Link to larger size should work now
     
  10. EWhytsell

    EWhytsell New Member

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    To do it the best possible way you'd need to take your series of shots at long exposure and as wide open as you can. Then you need to mask in a properly exposed city scene after processing the star trails to your liking.

    When shooting dim points of light aperture rules. In astronomy there is a thing called limiting magnitude and thats something that photogs don't need to think about on earth. A 70mm front glass has a limiting magnitude of around mag 11 (assuming the widest F stop can use nearly all the glass.) Human eye sees about mag 6. The stars in your shot are largely mag 2-4 stars.
     

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