Why do my Nikon D5100 sky photos show a faint grid or diamond pattern?
Asked 12/6/2021
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2 answers
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When photographing a clear sky with a Nikon D5100, some images show a faint diamond/grid-like pattern, especially after increasing contrast or pushing shadows/blacks in post. The files were shot in RAW, and the pattern appears in multiple RAW converters (Apple Photos, Nikon software, RawTherapee). Example shots were made with an AF-S DX 55-200mm lens. What could cause this, and how can I test whether it comes from the sensor, lens, or RAW processing?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
4y ago
2 Answers
1
You can do an experiment to isolate the problem and possibly rule out something happening in the lens electronics.
First, if you have another lens, try it! I assume you would have done this already were it an option, but I mention it just in case.
Second, take an exposure with the lens off and point the naked sensor at something gray like the sky, so it stands out the same. If the noise is still there, it's probably that decade old sensor failing on you.
Originally by user102986. Source · Licensed CC BY-SA 4.0
user102986
4y ago
0
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This is most likely an artifact that becomes visible when a smooth area like blue sky is pushed hard in post, especially when shadows/blacks are driven several stops. Even RAW files are not always completely untouched sensor data, and demosaicing/noise-processing can reveal repeating patterns in low-detail tonal areas.
From the answers, lens profile correction may reduce how obvious it looks, which suggests processing can play a role. But to isolate the cause, do a simple test:
- Try another lens if you have one.
- Take a test exposure with the lens removed, aiming the camera at an evenly lit gray/sky-like subject.
If the pattern still appears, the issue is likely in the camera/sensor or its RAW pipeline rather than the lens. If it only appears with one lens, lens-related correction or electronics may be involved.
In practice, if the pattern is only visible after extreme editing, you may simply be exceeding the usable dynamic range of the file in that part of the image.
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