What is the Moiré?

Moiré is a visual phenomenon, interference fringes that occur on objects at certain intervals. Taking pictures in actual, rainbow-colored stripes occur between the subjects like the pictures on the side. This performance is called moiré phenomenon. For example, the phenomenon of water wave-like streaks on mosquito nets or curtains reflected by sunny weather is similar. Iridescent streaks will occur when taking photos after wearing striped clothes.

When the pixel spatial frequency of the photographic equipment is close to the spatial frequency value of the stripes in the captured image, moiré will appear in the image.

Moiré phenomenon is a manifestation of the beat principle. When two patterns with spatial frequencies overlap, another new pattern is usually generated. This new pattern is usually called moiré ripple. Due to the CCD (image sensor) target surface (photosensitive surface) of the camera, and the large LED screen is composed of dot-matrix luminous tubes arranged in line, the entire large LED screen does not emit a large area, forming a grid-like pattern If they overlap, a moiré pattern is formed.

The main effect of the moiré phenomenon is the TV camera. If the existing large LED screen has uneven light emission between pixels, poor imaging effect, and dazzling at close range, moiré will appear, which will affect the promotion and use of the large LED screen in the studio.  

LED display screen has been widely used in many areas such as studios, monitoring center, shopping mall, exhibitions and so on. In fact, no matter outdoor or indoor LED display all have inherent advantages over other kinds of displays in aspects including brightness, definition and customized features. However, Moiré effect LED screen sometimes is a confusing and annoying problem when we use mobile phones or other shooting equipment to shoot the screen. That can be seen as strips like water waves in strange color, and also fussy tomographic images like the picture shown below:

Ways to get rid of the moiré phenomenon

1. Camera pixel bias technology

The moiré phenomenon is caused by the image detail being smaller than the interval between each image sensor. The spatial offset improves the horizontal resolution of the CCD camera brightness as much as possible. However, this method still cannot completely eliminate the moiré of the large LED screen, because the image sensor still has a certain spatial frequency and cannot be continuously formed into one surface.

The front filter is installed directly in front of the CCD, so that the exposure conditions meet the spatial frequency, and the high spatial frequency parts of the image are completely filtered to reduce the chance of moiré on the LED display.

2. Optical processing screen eliminates moiré

Fixed an optically processed screen closely to the surface of LED display, the special screen contains certain proportion of light absorbing material and a bead lens coating.

Through the optically processed large led screen, the camera can take pictures that do not produce moiré at almost any angle, any position, and any focal length. The optically processed large led screen, its brightness and color temperature meet the requirements of TV shooting, and there will be no moiré interference.

3. Adjust the camera when taking photo or video

(1) Change the camera angle. Since the angle between the camera and the large LED screen will cause moiré, slightly changing the angle of the camera (by rotating the camera) can reduce or eliminate moiré.

(2) Changing the focus, too clear focus and details on the detailed pattern may cause moiré, and slightly changing the focus can change the clarity, which helps eliminate the moiré on the large led screen.

(3) Lower the shutter speed. Lowering the camera’s shutter speed will help compensate for the low refresh rate of the LED screen, which will reduce the horizontal bar effect.

(4) To change the focal length of the lens, use a different lens or focal length setting.

(5) Process with software, such as Nikon Capture or Photoshop plug-in etc. to eliminate any moiré appearing on the final image.