Beginning of the problem : LTPO-OLED
Apple released Apple Watch 4 on September 2018 and many hype around it since it has the all new edge-to-edge display, similar to iPhone X last year. However, Apple is also experimenting with LTPO-OLED this time. LTPO-OLED combines the technology from LCD and OLED to make it has more efficient power consumption.
As we know, OLED can have a great power-saving if you use black background, since each individual pixel will be turned off. On the other hand, while you are watching videos and driving the pixel from black to colored color, it will requires more power on OLED since you will be constantly turning on and off each pixel. Using LCD technology there is a backplane to control all of this thing that makes it easier, however that means there will be no way to turn off the backplane and you won’t have pitch black contrast color.
Apple combines this backplane technology to OLED. The result is smaller battery on Apple Watch 4 and still the same up to 2 days battery life. However, there is a disadvantage to this technology. The screen density will be compromised. Meaning that it won’t be suitable for big screen like an iPhone. However, we might yet to see if Apple can make no compromise on screen density or not next year, since it will be a great help for battery life on the iPhone.
PWM Pulse Width Modulation
Apple has included PWM on their OLED iPhone to help control the brightness. PWM works by setting frequency on the LED to light at certain pulse. There are drawbacks on this technology, those are the screen flicker and the size. If you see an iPhone from camera, you will see that it flickers. Some people has more sensitivity to this flicker and can cause dizziness. The size of this technology is also considered big, making it no way to put it on an Apple Watch especially after putting those LTPO. Here’s the root cause of the uneven brightness on Apple Watch 4.
Since it has no PWM, the factory has to calibrate each individual pixel for Apple Watch to make it almost similar and every factory has margin of error number. Each pixel contains RGB-LED and they have to calibrate this 3 LED to display correct white color on each pixel. Unfortunately, my Apple Watch suffers from the calibration issues. The right side of the watch is not calibrated as same level as the left one. It could be seen directly if you are in dark room that the right side is brighter. Similar too the picture below.
Solution for this issue
Although, it will not interfere with your usage on daily basis, but if this annoys you, you could go to Apple Store and ask for refund or exchange if you are within the 14 days period. Other than that, you could also send your watch to Apple Repair Center which will probably be free but you have to be watchless for around 2 weeks. As I am writing this article, I have found that 2 of my friends also have this problem. Me myself is in my second replacement unit and it works fine. So I believe if you buy the current batch, it should be better. Since me and my friends that have this issue, bought the watch on the first to second batch.