The actual refresh rate also depends on the resolution, as a greater bandwidth is required to display the same resolution at a higher refresh rate. The controller driving the monitor must also be capable of using these refresh rates. Resolution This is affected by dot pitch and bandwidth. The dot pitch is distance between adjacent RGB phosphor dot groups, the smaller the dot pitch, the better the potential resolution. The bandwidth required is proportional to the number of pixels per second.
Poor bandwidth can cause the picture to lack sharpness, and small characters to be illegible.
Focus Focus is difficult to measure, but look for variations in sharpness between the centre and edges of the screen. High end monitors may have 'dynamic focus' and 'dynamic beam forming' which will help to reduce focus problems. The monitors power supply is also very important. When the screen changes brightness, for example going from a very dark image to light one, the monitor's power supply has to work harder, and if the supply is not well regulated, the voltage may drop, affecting picture shape. Viewing video particularly requires a stable power supply Magnetic Fields Monitors are susceptible to magnetic fields, to the extent that monitors designed to work in one part of the world will show colour patches in another part due to differences in the earths magnetic field, so be careful when placing speakers near monitors.