A screen that looks perfectly normal to the naked eye appears in a rainbow and wavy pattern for a number of reasons.
This situation appears a little differently on some screens. Especially on CRT (known as tube) monitors, a “horizontal and thick bar” starts to flow vertically quickly (as in Mor ve Ötesi’s I Have a Problem).
You are no stranger to this image. A computer screen that looks different in reality and on camera:
Before explaining the reason for this, we need to explain the working logic of the screens of digital devices. In fact, the screen of your laptop, monitor, TV or phone is constantly changing.
All these devices have a “refresh rate” at different rates. The refresh rate is how often the image on the device’s screen changes per second. This speed differs between screens. The following refresh rates are generally used today:
- TVs: 75Hz-120Hz
- Computer monitors: 60Hz-360Hz
- Phones: 50Hz-120Hz
You think you’re seeing a moving image on the screen, but the image itself isn’t actually moving.
A large number of frames pass by that appear incredibly fast on the screen, which your brain then corrects, suggesting that something is actually moving on the screen. The higher the frame rate per second, the more believable the motion will appear on screen.
Now that you know how computer and TV screens work, let’s take a look at how cameras work.
Here it is necessary to know how the “shutter (shutter) speed” works. Shutter speed is the amount of time the shutter stays open during an exposure. It means how much time your camera took to take that photo. The longer it takes, the blurrier the photo will be (if you’re trying to take a photo of a moving object).
Most modern DSLR and mirrorless cameras have a very fast shutter speed, ranging from 1/4000 to 1/8000. This means that it takes 1/8000 of a second for the camera to capture the image.
Now let’s come to the place where the zurna calls zırt:
As we mentioned earlier, the image on your TV/computer screen is constantly changing between 50Hz and 360Hz. We also talked about how the shutter speed on cameras works. Now, when we put this information together, a light bulb will turn on in your brain.
A camera with a slow shutter speed will capture the screen in the middle of the refresh process. The higher the refresh rate of a screen, the smoother the image.
Let’s take a look at the OLED screens on phones:
On some displays of this type, the brightness is adjusted using the pulse width modulation (PWM) method. The screen backlight turns on and off continuously at high speed (as we mentioned in the example above).
For example, if the screen brightness is 40%, the backlight works with a 40% duty cycle. This means that the screen is refreshed with 40% bright segment and 60% dark segment every cycle. Because the camera – unlike our brain – can detect these dark parts, ripples or lines appear in the viewfinder or in photographs.
If the screen brightness is 100%, this problem will not occur as the bright parts will be 100%. So before taking a picture of the phone’s OLED screen, set the screen to maximum brightness.
We also need to mention another phenomenon that causes this situation:
Screens are a grid of pixels. A digital photograph is also a grid of pixels. When these overlap, a moire pattern is formed.
Some of these pixels overlap, while others do not. Therefore, waves and stripes are formed. Just like in the screenshot below:
You can see the same effect with two window curtains standing in a row. Even some garments, such as sweaters, may appear wavy in videos for the same reason.
So why don’t we see this problem on screens in movies?
Movies are shot at 24fps; that is, while watching a movie, you will see 24 still images (frames) projected onto the screen in one second. Action movies and video games have higher frame rates to make the action look even smoother.
This problem is avoided in movies by synchronizing the refresh rate of the screen and the shutter speed of the shooting camera. In the same way, you can take better photos and videos by providing this equality. You can adjust these speeds in the settings section of your computer or phone/camera. You can also try adjusting the brightness, contrast and distance.
Sources: Camera Gurus, Science ABC, WIRED, Consumer Huawei
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