Good job It's a bit bright for my tastes too, but I had a quick look in Photoshop and there's plenty of good data to stretch the histogram a bit using levels. The comet and colours really pop off the background sky if you increase the contrast a little.
Thanks for your comments. There was fog and the exposure time is longer, I thought that's the reason why the pic is bright. And I adjusted it in Photoshop, but I'm not familiar with PS. The pic is single pic. I took 6-7 for the comet. If anyone want to process it, please leave me your email. I could send the original pics to you (unfortunately, they are .jpg, not .raw from Canon 500D camera).
Try using the Levels command with input levels of 50, 0.75, 245 - you'll see that the contrast increases dramatically, making the comet easier to see. The reason auto contrast/levels wouldn't work as well is that there's a big black silhouetted area that Photoshop won't "clip" - i.e. there's a big peak between 0 and 10, and then a flat part of the histogram between 10 and 50.
Try using the Levels command with input levels of 50, 0.75, 245 - you'll see that the contrast increases dramatically, making the comet easier to see. The reason auto contrast/levels wouldn't work as well is that there's a big black silhouetted area that Photoshop won't "clip" - i.e. there's a big peak between 0 and 10, and then a flat part of the histogram between 10 and 50.
