The most important aspect of a monitor is that it should give a stable display at the chosen resolution and colour palette. A screen that shimmers or flickers, particularly when most of the picture is showing white (as in Windows), can cause itchy or painful eyes, headaches and migraines. It is also important that the performance characteristics of a monitor be carefully matched with those of the graphics card driving it. It’s no good having an extremely high performance graphics accelerator, capable of ultra high resolutions at high flicker-free refresh rates, if the monitor cannot lock onto the signal.
Resolution is the number of pixels the graphics card is describing the desktop with, expressed as a horizontal by vertical figure. Standard VGA resolution is 640×480 pixels. This was pretty much obsolete by the beginning of the new millennium, when the commonest CRT monitor resolutions were SVGA and XGA – 800×600 and 1024×768 pixels respectively.
Monitor Refresh Rate
Refresh rate, or vertical scanning frequency, is measured in Hertz (Hz) and represents the number of frames displayed on the screen per second. Too few, and the eye will notice the intervals in between and perceive a flickering display. It is generally accepted – including by standards bodies such as VESA – that a monitor requires a refresh rate of 75Hz or above for a flicker-free display. A computer’s graphics circuitry creates a signal based on the Windows desktop resolution and refresh rate. This signal is known as the horizontal scanning frequency, (HSF) and is measured in KHz. A multi-scanning or autoscan monitor is capable of locking on to any signal which lies between a minimum and maximum HSF. If the signal falls out of the monitor’s range, it will not be displayed.
Calculating Maximum Refresh Rate
Where VSF = vertical scanning frequency (refresh rate) and HSF = horizontal scanning frequency the formula for calculating a CRT monitor’s maximum refresh rate is:
VSF = HSF / number of horizontal lines x 0.95
So, a monitor with a horizontal scanning frequency of 96kHz at a resolution of 1280×1024 would have a maximum refresh rate of:
VSF = 96,000 / 1024 x 0.95 = 89Hz.
If the same monitor were set to a resolution of 1600×1200, its maximum refresh rate would be:
VSF = 96,000 / 1200 x 0.95 = 76Hz.
- The Anatomy of a CRT Monitor (and CRT TVs)
- CRT Monitor Resolution and Refresh Rates (VSF)
- Monitor Interlacing
- What is the Dot Pitch of a Computer Monitor
- Dot Trio Monitors
- Grill Aperture Monitors
- Monitor Technologies: Slotted Mask
- Enhanced Dot Pitch Monitors
- Electron Beam Monitors
- Monitor Controls
- The Different Types of CRT Monitors – From ShortNeck to FST
- What is a Digital CRT Monitor and How Does It Work
- What is LightFrame Technology?
- Safety Standards For Computer Monitors
- TCO Monitor Standards
- Monitor Ergonomics