RGB vs. PenTile: How Subpixel Layout Affects Diagnostics

Published by BlackScreen Engineering Lab • January 9, 2026

Abstract: This paper analyzes the spatial distribution of sub-pixels in contemporary display panels. We compare the industry-standard Stripe RGB layout used in most LCDs with the Diamond PenTile and WRGB arrangements found in mobile and television OLEDs. The study highlights the impact of sub-pixel geometry on text rendering, effective resolution, and the detection of sub-pixel hardware faults.

When you use a Display Test to find a "dead pixel," you are often actually looking for a sub-pixel failure. However, the physical appearance of this failure changes drastically depending on the panel's internal architecture. Not all pixels are created equal.

1. The Gold Standard: Stripe RGB

Most computer monitors and laptop screens use the Stripe RGB layout. In this arrangement, every pixel consists of three equal-sized rectangular sub-pixels: Red, Green, and Blue, placed side-by-side.

Benefit: Excellent text clarity and 1:1 mapping for digital signals.
Diagnostics: A dead sub-pixel in an RGB Stripe panel is easy to identify because it occupies exactly 1/3 of a uniform square pixel.

2. The PenTile Matrix (OLED Dominance)

Developed to combat the faster degradation of organic blue material, the PenTile Diamond layout (popularized by Samsung) uses sub-pixels of different sizes and shapes. In this matrix, there are twice as many Green sub-pixels as there are Red or Blue ones.

Because humans are more sensitive to Green light for luminance perception, PenTile "shares" sub-pixels between adjacent logical pixels. This leads to a higher Luminous Efficiency but a lower Effective Resolution.

2.1 The "Fringe" Effect in Testing

When performing a Dead Pixel Test on a PenTile OLED (like on an iPhone or Galaxy device), a single sub-pixel failure may not look like a clean "dot." Instead, it might look like a microscopic "slash" or a dimmed area due to the non-linear sub-pixel rendering (SPR) algorithms used by the display controller.

Engineer's Insight: To audit a PenTile screen professionally, always use a magnifying loupe. Because of the diamond sub-pixel shape, what appears to be "noise" on a Black Screen is often just the sub-pixel rendering trying to compensate for an exotic sub-pixel geometry.

3. WRGB: The LG Television Approach

LG’s large-format OLED TVs utilize a WRGB layout. They add a fourth, pure White sub-pixel to the standard mix. This white sub-pixel is used to boost peak HDR brightness without over-stressing the organic red, green, and blue materials.

Diagnostic Note: On WRGB panels, a "White Screen" test might look exceptionally uniform, but you must check the White sub-pixel independently from the RGB mix to ensure the HDR luminance headroom isn't compromised by a single cell failure.

4. Why Geometry Matters for Color Uniformity

The physical gap between sub-pixels (the "Black Matrix") determines the Screen Door Effect. Panels with exotic geometries (like Delta or BGR) can cause color fringing on fine lines. During a diagnostic uniformity grid test, these geometric differences are what cause certain monitors to look "sharper" than others, even if they share the same 4K resolution.

Conclusion

Understanding sub-pixel geometry is the difference between a casual user and a display professional. As panels move toward micro-LED and tandem OLED structures, the complexity of sub-pixel arrangements will only increase. By utilizing native rendering tools that bypass OS-level scaling, you can see the raw output of these sub-pixel structures and accurately judge the hardware quality of your investment.