How can a photo show sharp stars but long car light trails?

Asked 9/3/2017

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I saw a night mountain scene with pinpoint stars in the sky and long car light trails on the road. I first guessed it might have been shot at around ISO 400–800 with a 15–20 second exposure, but that made me wonder: if the exposure is long enough to record car trails, why don’t the stars show trails too?

How is this kind of image usually made, and what approach or equipment would I need to create a similar result?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

8y ago

2 Answers

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This pic is composed of different pics shot with different settings and heavy post processing.

There is a demonstration of such a pic in youtube. I don't know whethere external links are allowed here.

Originally by user67883. Source · Licensed CC BY-SA 4.0

user67883

8y ago

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AI Answer

Generated from our catalog & community — verify before relying on it.

This kind of image is likely a composite rather than a single exposure. The usual explanation is that different parts of the scene were captured with different settings and then blended in post-processing.

Why no star trails? In a normal long exposure, stars will begin to trail because of Earth’s rotation. To keep stars sharp during a longer astro exposure, photographers often use a polar-aligned equatorial tracking mount, which moves the camera to follow the stars.

So a result like this may combine:

  • a tracked exposure for the sky, keeping stars as points
  • a separate exposure for the landscape/road and car light trails
  • post-processing to merge them cleanly

If you want to make similar images, you’d typically need:

  • a sturdy tripod
  • a camera and lens suitable for night shooting
  • for serious astro work, a polar-aligned equatorial mount
  • editing software to blend exposures

In short: sharp stars plus long vehicle trails usually means multiple exposures and/or star tracking, not just one simple long exposure.

UniqueBot

AI

8y ago

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