Standing crystals and crossed filters
Vertical alignment (VA) is one of the main ways to arrange liquid crystals in an LCD. Its defining feature is what the crystals do when no voltage is applied. In a VA cell, the elongated crystal molecules stand roughly perpendicular to the glass, pointing straight through the layer, instead of lying flat.
The cell sits between two polarizing filters whose orientations are set at right angles to each other. Light from the backlight is polarized by the first filter. If the crystals stand upright and do not change the light’s polarization, the second filter blocks it. The result is a dark subpixel. The basics of how liquid crystals control light apply here, with this arrangement as the specific variation.
To brighten a subpixel, a voltage tilts the crystals. Tilted molecules alter the polarization of the passing light, so more of it gets through the second filter. More tilt generally means more light.
Why blacks look deep
When the screen is viewed straight on and the subpixel is off, the upright crystals do little to the light, and the crossed filters block nearly all of it. The leftover light is small, so the black level is low. Since contrast ratio compares the brightest white with the darkest black, a lower black level tends to produce a higher contrast ratio. Because the numbers depend on how the figure is measured, they are best compared only between measurements made in the same way.
In general terms, VA panels have often measured with higher native contrast than IPS or TN panels of the same era, which is why they have been popular for televisions viewed in dim rooms. Results vary by individual product.
What it costs at the sides
The deep black depends on the crystals and filters lining up for a viewer looking straight at the screen. From an angle, light passes through the cell along a longer, slanted path and meets the crystals at a different orientation. The blocking becomes imperfect, so dark areas look lighter and the contrast drops. Colors can also change.
Two effects are commonly noticed:
- Gamma shift: the relationship between signal level and brightness changes with angle, so midtones appear to wash out or darken in ways that differ from the straight-on view. The idea of the gamma curve explains why this changes the whole look of an image.
- Color shift: reds, greens and blues do not fade equally, so skin tones and grays can take on a tint when seen from the side.
Makers use tricks to soften this. Many VA panels divide each subpixel into domains where crystals tilt in different directions, so that errors from one direction partly cancel those from another. This helps but does not remove the effect. The general topic is covered in viewing angles and why colors shift.
Speed and the dark-transition problem
Another trait is response in dark areas. Moving crystals from the fully upright state to a slightly tilted one can be slow in some VA designs, because a small voltage change produces a small push. Dark-to-dark transitions can therefore leave visible smearing or trails behind moving objects, especially in dark scenes. Manufacturers often apply overdrive, which momentarily boosts the voltage to speed things up, but too much can create bright halos. Summary response time figures typically leave out these details, as discussed under response time and motion blur, so the experience can differ from the numbers.
Curved screens and other uses
VA panels are common in curved monitors. A curve brings the edges of a wide screen closer to a sitter’s eyes, which reduces the angle between the line of sight and the screen, partly offsetting the off-angle weaknesses. This is one reason you often see the combination of curved ultrawide shape and VA. The benefit depends on seating distance and screen size.
Other places VA turns up include:
- televisions meant for dark or dim rooms,
- gaming monitors that prioritize contrast over wide-angle consistency, and
- some automotive or industrial screens, where requirements are set by the specific application.
For several viewers sitting at different positions, such as a family sofa, the angle behavior matters more than it does for a single person at a desk. With a mini LED backlight, VA contrast can be pushed even further, though local dimming brings its own quirks.
Comparing it with its neighbors
The sharpest contrast with VA is in-plane switching, where crystals lie flat and rotate within the plane of the glass. That layout keeps color steadier across angles but typically lets more light leak in dark scenes. The older twisted nematic design is fast and inexpensive but has narrower angles. No single design excels at everything, and recent improvements in each have narrowed some of the gaps.
Choosing sensibly
If you mostly sit directly in front of a screen in a dim room, watch movies or play games, and care about dark scenes, a VA panel can be a good match. If you edit images, need steady color over a wide viewing area, or share the screen with several people, the off-angle behavior may be a drawback. Checking a screen from the angle you will actually use it is often more informative than reading a specification.