PenTile for Digital Still Cameras (DSC)

There was a very thorough review of the Samsung NX10 camera on dpreview which uses a 3.0-inch VGA PenTile RGBG OLED display.  This review covers every aspect of this camera including the display.

I would like to only make a couple of minor corrections to this reviewer’s comments.

1.  PenTile technology was not used for this camera display to save power.  OLED can be intrinsically low power if the user interface is design to be predominantly black with white or bright text or graphics.  OLEDs do not consume power where they are not being lit up.  Unlike smartphones where users are accessing any and all pages on the web, the for a DSC can be entirely designed by the manufacturer and can take maximum advantage of this property of OLEDs.

Instead PenTile technology is applied here to enable such high resolution while maintaining such good brightness and a display  lifetime equivalent to lower resolution displays.

2. The author says

The other difference is that, rather than using a red, a green and a blue triplet of dots to represent each pixel, it uses pairs of sub-pixels to present the same information, in a way that is claimed to be visually indistinguishable. This technology, originally developed by a Californian company, is now owned by Samsung. As explained in this white paper, the screen offers the same resolution in luminance terms as a conventional screen. What isn’t made quite so clear is that you don’t have full color information at each pixel (because you’ve effectively got 640×480 green sub-pixels and two offset 320×480 matrices of blue sub-pixels and red sub-pixels).

Nouvoyance never says that PenTile is visually indistinguishable. We do say that it is equivalent in resolution per the VESA spec offering the same resolution as an equivalent RGB stripe display.  The author then says we don’t have the full color information at each pixel.  This is not the case.  Subpixel rendering allows us to create luminance centers at every logical pixel on the screen in the full resolution–here at 640 by 480 VGA.  It is quite true that there are fewer red and blue subpixels than green, so the red and blue luminance information may be positioned slightly further from the center of the center of the pixel in some circumstances, but every pixel will have the correct and full luminance information.

The comment that PenTile doesn’t have full color information at each pixel is strictly speaking correct, but this has far less impact than those words convey.  There is full color resolution in the vertical and horizontal at every pixel, but there is a slight reduction in color information on the diagonal. It would not be possible to detect this for photographs.  For PenTile RGBG OLED there is a reduction in chrominance information on the diagonals, but it is not such a reduction that the human vision system (HVS) can detect this except for selective test patterns which would involve fully saturated red on black.  Keep in mind that the human vision system can resolve 50-60 cycles/degree of luminance information, but only 6 cycles/degree on the red/green line of colors and only 3 cycles/degree on the blue yellow line of colors.  For this reason the vision system cannot tell where each color subpixel is located relative to the logical pixel.  As an expert on cameras the author is probably familiar with how the camera sensor uses a Bayer pattern (see below) that functions in much the same way.   Similarly, JPEG compression uses the same difference in resolution of luminance and chrominance to achieve some portion of this compression.  In neither of these cases, do people claim that these implementations lack full color information.

Overall the review was excellent, but I wanted to set the record straight as to the purpose of PenTile OLED, what we claim for the merits, and what we achieve with this technology.

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