Why is the LED picture taken by mobile phone unclear and how to change it

1.Reason

When we point our mobile phones or other shooting devices at the LED screen, inexplicable water wave-like stripes, strange colors, and strange faults will occasionally appear, and the same is true in the photos taken. Apparently some people thought the current was broken, but it was not actually caused by this.

The stripes that look like water ripples captured by mobile phones. They have a scientific name of "Moiré effect". The explanation is that when using a digital camera to shoot a scene, if there is a dense texture, it will often appear Inexplicable water wave-like stripes appear.

The reason for the proliferation of moiré patterns is that the refresh rate of the LED screen used is insufficient. At the moment when the conclusion is drawn, some rows on the LED screen do not light up, resulting in a series of moiré pattern phenomena. The refresh frequency is often referred to as the screen's Hertz (Hz).

Most LCD in use today default to 60hz. Because the screen is not always glowing, but is refreshed every once in a while. For example, 60hz means it is refreshed 60 times per second. However, the human eye screen has a delay, so the human eye cannot detect any flicker on the screen at all.

When taking pictures of the screen on a mobile phone, most of them will have a relatively fast shutter speed. When the shutter speed is faster than the refresh rate, it can capture the screen refresh process that we cannot see with the naked eye, which will produce "streaks"

Only when the refresh frequency is greater than 2 times the camera shutter speed, the LED screen will not appear moiré.

At the camera's common shutter speed of 1/2000 second, the nearly 1000 refresh rate of the ordinary cross-flow driver IC and the 1920Hz refresh rate of the dual-latch driver IC are not enough to avoid moiré. Only high-definition and high-end PWM driver IC with a refresh rate of 3840Hz or above can ensure that moiré patterns do not appear when taking photos on an LED screen.

2. Photography tips to reduce or eliminate such distractions

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

(2) Change the mobile phone camera position. Moiré can be reduced by changing the angular relationship by moving left or right or up and down.

(3) Change focus. Too clear focus and detail on delicate patterns can cause moiré. Changing the focus slightly can change the clarity, which in turn can help eliminate moiré.

(4) Change the focal length of the lens. Use different lenses or focal length settings to change or eliminate moiré.

(5) Process with software, use Photoshop plug-ins, etc. to eliminate any moiré patterns that appear on the final image.

(6) Use a filter mounted directly in front of the CCD. The exposure conditions are generated to satisfy the spatial frequency and the high spatial frequency portion of the image is thoroughly filtered. This will reduce the chance of moiré and simultaneously reduce the sharpness of the image.