Why do dark horizontal bands appear when I photograph cafe lights with my phone?
Asked 5/15/2021
5 views
2 answers
0
When I photographed bright decorative lights in a cafe with a Samsung Note 20, dark horizontal bands appeared across the lights. I saw it with both the front and rear cameras. If I partially blocked the lights with my hand, the bands became much less visible.
One example was shot at f/2.2, 1/588 s, ISO 50. Another similar shot was at 1/130 s. Why does this happen, and is it caused by the lights, the phone camera, or something on the lens?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
38
The lights are either fluorescent or LED. This means that they turn on and off 50/60 times a second depending on the country.
The camera scans across the sensor at a relatively slow (constant) rate, but the photosites sample the incoming light for longer or shorter times depending on the scene (this time is equivalent to shutter speed). This is an exposure method called "rolling shutter" and is common with electronic shutters.
The first image with the dark bars uses a fast 'shutter speed' and shows the light/dark cycle of the light pretty clearly. The second image has some of the light blocked by the hand, and so uses a slower 'shutter speed' which is near one light/dark cycle multiple long and mostly evens out the lighting.
Originally by user11772. Source · Licensed CC BY-SA 4.0
user11772
5y ago
0
Generated from our catalog & community — verify before relying on it.
The most likely cause is flicker from the light source interacting with your phone’s electronic/rolling shutter.
Many LED and fluorescent lights don’t emit perfectly steady light—they pulse with the AC power frequency. In South Korea that’s typically 60 Hz, and some lights effectively flicker at a multiple of that. A phone sensor is often read line-by-line rather than exposing the whole frame at once, so at faster shutter speeds you can record different brightness levels in different rows, which shows up as dark bands.
That fits your examples: the 1/588 s image shows stronger banding, while the slower 1/130 s exposure averages more of the flicker cycle so the bands are reduced. Blocking part of the light with your hand also lowers the contrast, making the bands less obvious.
It’s probably not dirt on the lens. Another answer suggested a wire/grid in front of the scene, but with the information given, light flicker plus rolling shutter is the better explanation.
To reduce it, try a slower shutter speed, anti-flicker mode if your camera app has one, or avoid problematic LED/fluorescent lighting.
Recommended products
UniqueBot
AI5y ago
Your Answer
Related Questions
Why do black bands appear when photographing an AMOLED phone screen?
Why does a white product photo look blue and show horizontal gray bands under LED lights?
Why do my Nikon D5500 photos look less sharp than my smartphone's?
Why do LED lights cause banding with silent shutter, and why is the Sony A9 less affected?
Why am I getting a dark horizontal band with a Canon 7D and 580EX II below sync speed?