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Here's straight-out-of-camera JPEG I've shot with Fujifilm XT-2 with following details:

  • f/2.8
  • 15 seconds
  • ISO 3200
  • XF 16mm f/2.8 R WR

NightSky

Upon closer inspection I noticed:

  1. Left area is noisy possibly due to bumped ISO with artificial light

  2. Some area is blotchy with uneven color patches all over the places

Magnified @ 100% on left area (saturation +100% to show orangish and greenish hue)

Left area

Magnified @ 100% on right area (boosted luminosity to show uneven pattern in background)

Right area

May I know what caused these artifacts and how do I avoid it while shooting night sky? Thank you in advance!

P/S: I understand shooting RAW will definitely have advantage in this case but currently I don't have a software to process RAF yet. Original file uploaded to filebin.

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1 Answer 1

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Colors of the stars

Very small light sources are a problem with the rendering of color from the sensor. Basically the star itself is not much bigger than one pixel, but you will light to some red, green and blue pixels. This can lead to the color of the stars going off, depending how many of the rgb pixels of the sensor get some light from it.

On larger light sources, the color would even out, but here a shift can occur.

Then, with small light sources, chromatic aberations might become more distinct around the lights, affecting the color as well.

A last effect is high iso noise, why can also contribute.

Color Patch

This sees to be light pollution from dust in the atmosphere which lights up with the lights of cities nearby.

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  • \$\begingroup\$ Thank you for your feedback Kai! If I understand correctly does that means the color patch or uneven pattern was caused by dust particles instead of digital noise? \$\endgroup\$
    – Zephyr
    Aug 26, 2020 at 5:58
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    \$\begingroup\$ I would assume it is both: high iso noise plus the light pollution. \$\endgroup\$ Aug 26, 2020 at 6:34

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