Sensor Banding

Phenomenon Description

Sensor banding, also known as flickering in some cases, refers to obvious screen flickering and jumping water ripple-like stripes in the video.

Specifically, it may manifest in the following forms (not all symptoms occur simultaneously):

Different rows in a single frame present inconsistent brightness, showing alternating light and dark stripes;

The same rows across different frames vary in brightness, resulting in jumping water ripple patterns in the video;

The overall brightness fluctuates obviously between consecutive frames with noticeable light and dark transitions.

Variation Law of Alternating Current

Alternating current (AC) follows a sine wave pattern with two common frequencies: 50 Hz and 60 Hz.50 Hz is adopted in China, Thailand, India and most European countries, while 60 Hz is used in the United States, Canada, Mexico and other regions.

Taking 50 Hz as an example: AC completes a full cycle every 1/50 second (20 ms).Since light energy has no positive or negative polarity, the actual energy cycle is halved to 1/100 second (10 ms).

Therefore, the brightness of traditional incandescent lamps powered by AC fluctuates continuously at a 10 ms cycle. Such rapid brightness changes are imperceptible to the human eye.

Rolling Shutter

Common image sensors are divided into rolling shutter and global shutter types.

A rolling shutter sensor exposes pixel rows sequentially rather than capturing the entire frame at the same time. This creates a time offset between the exposure moments of different rows.Exposure can be regarded as brightness integration; the integrated light quantity directly determines screen brightness.If ambient light brightness changes during exposure, different rows will capture inconsistent light levels, eventually causing banding artifacts.

Cause Analysis of Different Flicker Phenomena

Analysis of Different Rows in One Single Frame

1. Exposure time: 10 msAssume Row M and Row N start exposure at time tm and tn respectively, with the same 10 ms exposure duration. The shaded area in the figure represents the integrated light volume of each row.

Analysis of the Same Row Across Different Frames

---

Summary Conclusion

No banding occurs when the exposure time is an integer multiple of the light source energy cycle;
When the exposure time is not an integer multiple of the energy cycle, row brightness deviation and water ripple banding are inevitable. Whether the stripes scroll depends on the frame rate;
If the frame interval (1/FPS) is an integer multiple of the energy cycle, inter-frame brightness is stable, and static banding will not scroll; otherwise, vertical scrolling stripes will appear.

---

LED Banding Phenomenon

Core Differences Between LED and Incandescent Lamps