The 1080p Super AMOLED display on the Galaxy S4 is a brilliant feat of engineering. With over two million pixels crammed into a screen that is only 5 inches long diagonally Samsung have achieved a display with a pixel density of 441 ppi, blowing Apple's Retina Displays out of the water. While accomplishing these pixel densities with an LCD display is relatively simple and a proven technology, Samsung decided to pushed the envelope by designing an AMOLED display with the same resolution. As a result they suffered problems with low yields during the initial manufacturing process and were even rumored to be using a LCD panel for their new flagship. When the S4 was finally unveiled on March 14th at Time Square, Samsung showed off their new flagship phone along with its new cutting edge display which earned the praises from even the harshest display critics.
The new display panel on the Galaxy S4 does not use the standard RGB layout found on most displays, instead it still uses the RGBG Pentile display of its predecessors, but Samsung have tweaked the design of subpixel arrangement and provided Raymond Soneria, the president of DisplayMate with a closeup on the new layout. Below we have the standard RGB and RGBG Pentile layouts used in most displays.
Notice how in the standard RGB display (on the left) there is an equal number of red, blue and green subpixels. This layout is found in all LCD displays and the Super AMOLED+ display found on the Galaxy S2. Also note how all the subpixels are the same size. Now on the right we have the standard Pentile display where the pixel layout alternates red, green, blue, green (RGBG), resulting in 50% less red and blue subpixels, thus saving space on the display. Another benefit of such a layout in an AMOLED display is the increased efficiency because blue subpixels are incredibly inefficient using ten times as much energy as a green subpixel to obtain the same level of brightness, so by maintaining a higher number of more efficient subpixels you can obtain the same brightness levels with lower power consumption. But the main reason for the emergence of the pentile layout though is subpixel ageing. Blue subpixels and red ones to a lesser degree are not as efficient as the green subpixels and as a result also burn out quicker, to counteract this Samsung make these pixels larger so they don't need to run at a high intensity in order to accomplish the same levels of luminosity. However because an individual pixel's color is determined by the intensities of the subpixels of all three colors, each set of two subpixels either green and red or blue needs to borrow the subpixel next to them inorder to properly display colours, while this isn't an issue for smooth gradient transitions, if there is a high contrast image it can lead to a blurry of text or images that is only prevalent in pentile displays.
Below is an image of the new diamond pixel pentile display found on the Galaxy S4:
As you can see this new layout has diamond-shaped subpixels instead of the usual square ones, while the difference between a square and a diamond is nothing more than a 45 degree rotation, this simple change allows Samsung to pack more subpixels in the same area because the space is now being used more efficiently by reducing the dead space between subpixels by increasing the geometric efficiency. By minimizing the space between pixels and increasing the pixel count Samsung hope to reduce the 'fuzziness' that is prominent of previous pentile displays.