There are so many brands, makes and types of displays on the market today that it is rather difficult to choose one for your living or home cinema room. In effect, there are 3 major things you need to look for when evaluating the quality of a display:
Contrast Performance
One of the most important aspect of perceived image quality is not resolution, as display manufacturers would like you to believe, but contrast performance. Contrast performance can be sequential contrast – also called on/off or inter-scene contrast – and intra-scene contrast, that is contrast within the same frame of video.
Because of this, contrast performance needs to be evaluated on dark as well as bright images and in moving from dark to bright images.
Contrast performance will also affect black level and can affect shadow detail performance of the display.
Let’s take the switch from old CRT TVs with great black levels to the then top of the range flat panel displays, which had rather poor black level performance in comparison. Normal low-resolution TV broadcast looked better on CRTs, while the new higher resolution flat panels needed specialised DVD players and trickery in signal processing to make images watchable.
The difference between poor and great black level performance.
The better the contrast performance of the display, the more three-dimensional the images will look on the screen.
If a display has dark inky blacks but it fails to resolve the subtle details in the darker areas of the image, the image will look flat especially on dark images or movie scenes. It is important that great black levels are married with great shadow detail performance to give a three-dimensional image regardless of the material.
Did you know that the brightness setting on your TV affects the black levels while the contrast setting affects the bright areas of the image? Just test the controls and notice what areas of the image change.
Brightness Performance
Even before resolution, how bright a display can go while maintaining its blacks contributes greatly to perceived image quality. The brighter the image can go, the more contrast your eyes will perceive – as there will be more contrast between the dark and bright areas of the image. The human eye will even perceive an image as higher-resolution simply because of the brightness of the image.
For projectors brightness plays an important part dependent on what kind of light control you have in a room. In a normal living room with imperfect light control and light walls, projector brightness is more important than black level performance. While in a completely light-controlled room with black walls, black level performance becomes more important than brightness. Ideally you want a display that can do both.
For 3D performance, you will want high brightness again.
Resolution
There are three things under resolution you need to look our for.
Native Resolution
Native Resolution: the actual number of pixels available on the display.
Please refer to the diagram below regarding the type of resolutions currently available on displays.
Resolutions of modern displays
The amount of pixels you need to keep the image looking great depends on your viewing distance from the screen. As a guide, at the average viewing distance of 3 meters, you will notice the benefit of:
1080p / Full HD panel for any display above 30″ (display size is measured in inches diagonally).
4K for anything larger than 70″.
This means there is no actual benefit of buying a display with a resolution below those sizes at the distance of 3 meters for the average person.
Scaling Performance
Another area you need to look out for is how the display handles scaling.
Scaling: the transformation of an image from one resolution to another. For example, a DVD or TV image which has a maximum native resolution of 576p to 1080p.
Although most new material is now on Blu Ray and therefore 1080p natively, we still watch content on lower-resolution formats such as DVD and broadcast TV. The display needs to be tested regarding how well it handles this scaling. Some displays do this poorly but otherwise they perform well. In that case, you can still buy playback devices such as DVD players or set top boxes that do the scaling to the display’s native resolution to improve the image to bypass the internal scaling of the display.
Motion Handling / Motion Resolution
The last aspect of resolution is motion handling. It is also called “motion resolution”.
Motion Resolution: how well a display maintains image sharpness with moving images.
Display manufacturers understand how important motion resolution is, so much so that they employ digital trickery called frame interpolation – to reduce motion blur to keep image sharpness. You will want to turn any such trickery off and evaluate the display’s native ability to switch its pixels on and off using the same source device, such as Blu Ray player.
How to correctly evaluate a display?
This is the tricky part: as much as the above areas can highlight a display’s native performance, it is actually an interplay of the source device AND the display that will give you the end result. What does that mean? You need to evaluate the display’s ability using similar playback devices that you will be using at home, such as DVD players, Blu Ray players, TiVo, Gaming Consoles, etc.
Also, you need to set these devices up correctly to get the best performance out of the display: settings such as output resolution, output frame-rate, colour system, etc.
Which display technology?
So which display technology excels at all areas? It turns out some do better in some areas than others and it depends on your preference and situation as to what’s going to serve you best. The best thing to do is look out for the three areas above and trust your own eyes.
Flat panels:
Normal LCD Displays:
- Great native resolution, brightness and colour reproduction
- Below average black levels
- Below average motion resolution
LED and OLED Displays:
- Great black levels
- Great brightness
- Great all-around resolution
- Motion-resolution dependent on manufacturer and product
Plasma Displays:
Yes, they are still around, although in small numbers.
- Great black level performance
- Good brightness
- Below average motion resolution
Projectors
DLP Projectors
- Class-leading brightness performance and motion resolution
- Great Colour reproduction – especially for 3-chip varieties
- Black level and shadow detail performance depends on manufacturer and product – goes from average to class-leading.
Recommended for brighter home cinema rooms as the high brightness will create a better perceived contrast. Also recommended for high-frame-rate material such as sports and 3D.
LCD Projectors
- Generally challenged black levels and shadow detail performance, although some manufacturers are better than others.
- Great brightness and colour reproduction
- Good but not great motion resolution.
Recommended when DLP projector is not suitable for viewers because of the DLP Rainbow effect.
XSDR – IDLA – LCOS
- Class-leading black level and shadow detail performance bettering even the best cinemas in the World.
- Historically low brightness over their lifetime more suited for dark home cinema rooms
- Motion-resolution has considerably improved but DLP still betters it.
Recommended for dedicated, light controlled home cinema rooms. The best cinemas use this technology for 2D viewing. DLP is still better for 3D.
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