How can I reduce sodium-vapor streetlight color cast in night photos of buildings?
Asked 10/3/2014
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I want to photograph buildings at night and add my own light with torches/flashlights, but nearby sodium-vapor streetlights are casting a strong yellow/orange color. Is there a practical way to reduce that cast? Can a filter help, and if so, what kind?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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See How does the colour of ambient lighting affect colour rendition?, because that question uses a sodium vapor light as an example. As the answers there explain, sodium vapor lights produce a very, very narrow spectrum of light:
CC-BY-SA image from Wikimedia Commons, author Philips Lighting
And in fact, this is effectively monochrome. Your only options are:
- add additional, non-monochromatic light — it sounds like you're doing that with torches
- accept that it's monochromatic, or at least very very skewed, and possibly convert to grayscale
- filter out the 600nm spike, and use a very long exposure to bring up any other ambient lighting to an acceptable exposure level
The exact filter you will need will depend on the exact lights in question, but the above should provide a good starting point.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
11y ago
0
Generated from our catalog & community — verify before relying on it.
Sodium-vapor lighting is difficult because it emits a very narrow spectrum of light, especially low-pressure sodium, which is nearly monochromatic yellow. That means white balance alone often can’t fully restore natural color, because the missing colors were never recorded.
Your practical options are:
- Add stronger broad-spectrum light of your own (torch/flash) so it dominates the sodium light.
- Accept the look, or convert to black and white.
- Use a filter that suppresses the sodium wavelengths. A didymium filter (often sold as a red-enhancer/light-pollution style filter) can reduce the common sodium emission around 589nm and may help with some other light pollution too.
- In some cases, filtering out that spike means you’ll need a longer exposure to bring up other ambient light.
If the streetlights are high-pressure sodium, results are less perfect because their spectrum is broader than low-pressure sodium.
Custom white balance or RAW correction can help reduce the overall cast, especially if you shoot a gray/white card, but it cannot fully recover accurate colors under strongly monochromatic sodium light.
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AI11y ago
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