Why VR Image is Bad? Screen Door Effect Coping With PenTile Hybrid Technology

Why VR Image Quality Matters

Have you ever wondered why VR images sometimes appear less sharp than expected? Or which VR goggles offer the best resolution? It’s not uncommon to hear that PlayStation VR surpasses Vive in terms of resolution, despite the former having a significantly lower pixel count. Let’s delve into the intricacies of virtual reality imaging.

But first, let’s clarify some key terms to avoid any misunderstanding regarding virtual reality:

1. Resolution – This refers to the number of pixels both horizontally and vertically that the graphics driver processes and displays. You may be familiar with adjusting resolution settings in games to maintain smooth performance. The resolution is the number of pixels that the graphics processing unit (GPU) processes, and this image is then displayed on the monitor, which also has its native resolution.
2. Pixel – A pixel is the smallest unit of an image that the display graphics card can project. However, the monitor further subdivides pixels into smaller elements known as subpixels. The handling of subpixels happens at the monitor’s end and is not the concern of the computer or GPU.
3. Subpixel – These are the components within a pixel that allow the creation of millions or even billions of colors by exploiting the physics of light. Subpixels come in various configurations, including RGGB, PenTile, Bayer, Quattron, and more.
4. SDE (Screen Door Effect) – This effect is a result of subpixels and the spaces between them. You can witness the SDE when closely inspecting a monitor with a magnifying glass, where the dark spaces between subpixels become noticeable.

One of the most bothersome issues in VR is the Screen Door Effect (SDE), which is more significant than the VR image’s resolution. Many individuals mistake subpixels for pixels and subsequently question the resolution of current VR technology. Some even claim that VR resolution needs to wait for 4K graphics. However, this is not entirely accurate.

Undoubtedly, VR image quality would greatly benefit from 4K resolution. Yet, even with current resolutions, image quality can significantly improve when the visibility of subpixels is reduced.

Why Green Pixels Are Less Affected?

Both the Oculus Rift and HTC Vive currently employ displays with a hybrid geometry known as PenTile, originally designed for smartphones to fit more pixels in a 1-inch space. Through certain design and manufacturing techniques, this technology has proven to work remarkably well for VR, offering a balance between affordability and image quality.

Additionally, the green subpixel in PenTile displays is smaller, which enhances color quality but also widens the gap between subpixels. Why are green pixels smaller? The human eye is most sensitive to green light in the light spectrum, meaning less energy is needed to visualize green pixels compared to blue or red subpixels.

As a result, the visibility of subpixels depends on the colors displayed on the screen, as subpixels are engaged to varying degrees based on the colors.

VR essentially functions like a magnifying glass, scaling a small screen to cover 100 degrees of our field of vision. Manufacturers employ various techniques to minimize the SDE, leading to varying results in VR image quality.

Currently, the Oculus Rift stands out for its hybrid optics (combining Fresnel lenses with traditional ones), effectively reducing the visibility of PenTile subpixels. The Sony PlayStation VR follows closely, although this assessment is not absolute, and the verdict may change based on personal experience with the devices.

Is PlayStation VR the Best in Terms of VR Image Quality?

Regardless of whether the PlayStation VR is the ultimate champion, it undeniably offers an impressive experience. In fact, many users may not even notice subpixels in devices like the PlayStation VR, similar to the experience on Oculus.

Let’s hope this clarifies the discussion around VR image quality. The key takeaway is that VR resolution is not the sole factor; subpixel visibility plays a critical role. So, it’s not just about the resolution; it’s about the overall visual experience.

And as a final note, please bear in mind that the SDE is only one aspect of VR image quality. Other factors such as the field of sharp vision, contrast, response time, and more contribute to the overall VR experience.