X-bit labs

Contemporary LCD Monitor Parameters: Objective and Subjective Analysis

Category: Other

by Oleg Artamonov

[ 01/23/2007 | 02:21 PM ]

In this article we will cover some specified parameters of monitors (how they are measured by the manufacturers, how relevant they are for practical uses, etc.) and some issues pertaining to the peculiarities of the human vision (this mainly refers to the response time parameter).

Table of contents:

• Response Time of Monitors and Eyes
  
• Input Lag
  
• Contrast Ratio: Specified, Actual and Dynamic
  
• Color Reproduction: Color Gamut and LED Backlighting
  
• Color Reproduction: Color Temperature
  
• Workplace Ergonomics and Monitor Setup
  

When it comes to the various parameters of LCD monitors – this topic is regularly discussed in our articles as well as on every hardware resource that deals with monitors among other things – three levels of discussion can be distinguished.

The basic level is, “Does the manufacturer try to fool us?” This question has a trivial answer. Serious manufacturers of monitors don’t come down to mere lies.

The second level is more complicated, “What do the declared parameters mean, anyway?” This boils down to discussing how the parameters are measured by the manufacturers and what practical constraints on the applicability of the measurement results there exist. For example, the response time parameter was defined in the ISO 13406-2 standard as the total time it takes an LCD matrix to switch from black to white and to black again. Tests prove that for every matrix type this transition takes the least amount of time whereas a transition between two tones of gray may take much longer and the matrix won’t look as fast as its specs suggest. This example doesn’t belong with the first level of discussion because the manufacturer can’t be said to lie to us: if you select the highest contrast setting and measure the “black-white-black” transition, it will coincide with the specified response time.

But there is an even more interesting level of discussion. It’s about how our eyes perceive this or that parameter. Putting monitors aside for a while (to return to them below), I can give you an example from the acoustics field. From a purely technical point of view, vacuum-tube amplifiers have rather mediocre parameters (like a high level of harmonics, poor pulse characteristics, etc), so they don’t reproduce sound accurately. However, many listeners are fond of the sound of tube-based equipment. Not because it is objectively better than that of transistor-based equipment (as I’ve just said, it is not true), but because the distortions it brings about are agreeable to the ear.

Of course, the peculiarities of perception only come into view when the parameters of discussed devices are good enough for such peculiarities to matter. You can take $10 multimedia speakers and they won’t sound any better whatever amplifier you connect them to just because their own distortions are grosser than the flaws of any amplifier. The same goes for PC monitors. When the matrix response time amounted to dozens of milliseconds, there was no point in discussing how the human eye perceives the onscreen image. But now that the response time has shrunk to a few milliseconds, it turns out that the monitor’s speed – not its specified speed, but its subjective speed as it is perceived by the eye – is not all about milliseconds.

In this article I will cover some specified parameters of monitors (how they are measured by the manufacturers, how relevant they are for practical uses, etc) and some issues pertaining to the peculiarities of the human vision (this mainly refers to the response time parameter).