Brightness and Contrast
The monitor has 100% Brightness and 50% Contrast by default. I selected 20% Brightness and 21% Contrast to achieve a 100nit level of white.
The P221W controls its brightness by means of modulation of the power of the backlight lamps at a frequency of 212Hz. Some users had reported a noticeable flicker at low brightness, but I didn’t observe this with my sample. To remind you, it is advisable to avoid single daylight lamps with electromagnetic ballast as the means of illuminating your workplace (such lamps are employed in inexpensive desk lamps, for example) because they flicker at the double frequency of the power mains (100Hz in my region). Coupled with the monitor’s backlight flicker at about 200Hz, this may lead to low-frequency brightness pulsation the eye can see. You should use ordinary incandescent lamps or fluorescent lamps with electronic ballast, like the popular energy-saving lamps, from respected firms such as Philips, OSRAM, General Electric, Wolta, etc.
At the default settings the monitor is 300 nits bright. This is too much for work, so you should lower it to comfortable level. The specific level is determined by the lighting of your workplace. You should lower the screen brightness smoothly, giving your eyes 15-30 minutes to get used to the specific level before judging if it suits you. A normal brightness is going to look too dim after you switch from the monitor’s default settings, but your eyes will soon adapt.
You can use the following method: the brightness of white on the monitor’s screen should be comparable to the brightness of a sheet of good white paper if you place it near the monitor.
The contrast ratio is very good at 1000:1 and higher.
The pictures based on the measurement results show that the monitor’s backlight brightness is quite uniform. There are no conspicuous dark or bright spots except for the darker band at the right of the screen.
As for specific numbers, the average uniformity of white brightness is 5.2% with a maximum deflection of 18.9%. For black, the average and maximum are 4.3% and 17.0%, respectively.