This article describes a phenomenon called, "Moiré" which occurs to all displays when photographing the screen.

Wavy lines or interference patterns in photos of a television screen or display monitor are often caused by a phenomenon known as moiré. Moiré occurs when two repetitive patterns, such as the pixel pattern of a display screen and the pattern of the camera's image sensor or the pattern of the photo subject, interact in a way that creates a new, unwanted pattern. This interference pattern manifests as wavy lines or a rippled effect in the photo.

Example of Moiré



The specific causes of moiré can vary, but some common scenarios include:

1. Resolution mismatch: If the pixel pattern of the display screen is close to or overlaps with the resolution of the camera's image sensor, it can create interference. For example, if the camera's sensor has a similar number of pixels to the display screen, the alignment between the two patterns may cause moiré.

2. Fine patterns or textures: The presence of fine patterns or textures in the subject being photographed, such as a grid-like pattern or tightly spaced lines, can coincide with the pixel pattern of the display screen, resulting in moiré.

3. Interference with anti-aliasing filters: Cameras typically employ anti-aliasing filters to reduce moiré effects in regular photographic situations. However, when photographing a display screen, the camera's anti-aliasing filter might not align perfectly with the screen's pixel pattern, leading to interference patterns.

To minimize or avoid moiré when photographing a television screen or display monitor, you can try the following:

1. Adjust the camera angle: Change the angle of the camera in relation to the screen to minimize the overlap or alignment between the pixel pattern of the screen and the camera's image sensor.

2. Adjust the camera distance: Experiment with the distance between the camera and the screen. Sometimes, moving closer or farther away can reduce the interference.

3. Use a different focal length: Changing the focal length of the camera lens might help minimize or eliminate the interference patterns. Try zooming in or out or using a different lens if available.

4. Use a polarizing filter: Adding a polarizing filter to the camera lens can sometimes reduce moiré patterns by reducing unwanted light and interference.

5. Adjust the display settings: If possible, modify the display settings of the screen, such as changing the resolution or adjusting the screen refresh rate, to minimize interference with the camera's sensor.

Despite these measures, it can be challenging to completely eliminate moiré in certain situations. If moiré still persists, post-processing techniques like using software tools to selectively blur or remove unwanted patterns can be applied to minimize the effect during photo editing.