Why does my Pentax K-x show heavy color banding and artifacts in low light?
Asked 3/16/2011
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My Pentax K-x produces strong color banding and strange artifacts in low-light shots. One example was taken at 0.3s, f/5.6, ISO 400, with JPEG output in sRGB. Noise reduction was set low/off, but the problem remained.
Relevant settings from the file metadata include:
- Exposure compensation: -1 EV
- Dynamic Range Expansion: On
- Shadow Compensation: Strong
- High ISO NR: inactive at ISO 400
- JPEG quality: Best
What camera settings could cause this kind of banding/noisy shadow artifacting, and how can I avoid it?
Originally by user4337. Source · Licensed CC BY-SA 4.0
user4337
15y ago
2 Answers
2
So, my current working theory is that you're seeing a combination of these factors:
- Underexposure: the image is set to a more-dark-than-average exposure (EV compensation set to -1).
- Dynamic Range Expansion is on. This increases shadow noise, because it works by underexposing by a stop and then pushing the exposure up while preserving highlights.
- Shadow Compensation set to "Strong". This further pushes up all of the dark areas, which in this case are basically useless and full of noise. (Your camera has a good sensor, but it can't work miracles when everything is stacked against it.)
- "Muted" image tone curve. This drastically reduces sharpness, contrast, and saturation, which probably isn't ideal given all of the rest.
In my experience with my Pentax K-7, the "strong" setting for Shadow Compensation is rarely useful, not just because it produces noise but because the results look unrealistic. A lighter touch in post-production is my preference.
The good news is that if you're shooting in RAW+JPEG, you can fix some of this after the fact — at least the shadow compensation and the tone curve. But the dynamic range expansion and EV compensation can't be changed after the fact. Don't be afraid of increasing ISO when it's dark out — see Matt Grum's interesting answer to this question, which argues that using the highest ISO possible actually reduces noise.
And maybe invest in a tripod, since clearly the SR wasn't enough for this shot. :)
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
15y ago
0
Generated from our catalog & community — verify before relying on it.
The most likely cause is not the color profile, but shadow noise being amplified by your exposure/settings.
Your shot is already underexposed (-1 EV), and Pentax Dynamic Range Expansion typically protects highlights by effectively underexposing and then lifting darker tones. With Shadow Compensation set to Strong, the camera then boosts those dark areas even more. In a low-light image, that can turn weak shadow data into visible color banding and ugly artifacts.
So the combination of:
- low-light scene
- underexposure
- Dynamic Range Expansion on
- strong Shadow Compensation
is the likely culprit.
JPEG compression does not appear to be the main issue here if the file was saved at the camera’s best quality.
To avoid this:
- turn off Dynamic Range Expansion in low light
- reduce or disable Shadow Compensation
- avoid unnecessary negative exposure compensation
- expose a bit brighter when possible without clipping highlights
- if available, shoot RAW for better recovery and less in-camera processing damage
In short: the camera is aggressively lifting noisy shadows from an already dark exposure.
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AI15y ago
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