All posts tagged modulation

Is Sharpness the Same as Graininess?

I recently came across this FoneHome article comparing the Galaxy S 2 Super AMOLED Plus to the HTC Sensation qHD and noticed that there seems to be some confusion about graininess and sharpness.

It is possible to have a grainy appearance and still have a sharp display.  And if so, how?

When people talk about a grainy appearance they are really speaking of pattern visibility. The structure of the subpixels can be seen, especially if the display is larger diagonal and the format is low. That is why PenTile is not applied to very low dpi applications. Since PenTile has fewer dots, but the same number of pixels, it is easier to see the pattern than in an RGB stripe display of the same format and size. I have met some people who have exceptional vision, or the ability to view displays from very close range, who can see such graininess even in the iPhone 4 display, so this is a very individual thing.

For qHD displays like the Motorola Atrix, it far more difficult to see the pattern. There are, for example,  3.1-inch PenTile OLED displays where nobody has ever commented in any blog on any graininess or that these phones use PenTile technology.

So can a grainy display still be sharp? Yes, sharpness is measured and perceived as modulation ratio. When you write a black and white line pair can you still see the difference between the white and the black and you must be able to measure 50% contrast modulation or more. PenTile displays have no difficulty meeting and exceeding 50% contrast modulation ratio to the full resolution of the panel and in any direction. So a WVGA panel should be capable of 400 black and 400 white lines in one direction and 240 black and 240 white lines in other direction. This is possible because the algorithms for PenTile display analyze each image and apply adaptive filters to enhance edges of text and fine line graphics, thereby assuring sharpness.

In short, the answer is yes; a display that may look a bit grainy can still be sharp.
Hopefully that helps clear things up (no pun intended).