- Oct 30, 1997
- Aberdeen, MD & Navesink, NJ
- Real Name
- Sam Posten
And it sort of is and sort of isn't 'fake' pixel shifted 4k.
Evan Powell, Editor
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I guess I should write a separate piece on this, but to clarify, the pixel shift technology used by Epson and JVC is essentially different than the way the 4K DLP chip operates. It is not correct to think of the DLP process as pixel shift in the same sense as it is on 3LCD. On the 3LCD pixel shift machines, a 1920x1080 image is scanned on the first pass, then a second 1920x1080 image is off shifted diagonally by about half a pixel up and a half pixel sideways and overlaid onto the first scan. So it does not create a completely separate field of discrete pixels on screen on the second pass like the DLP chip does. This happens so fast that the eye cannot detect it, in the same way that interlaced scanning on CRTs is not visible. The advantage is that the first and second scans can be two slightly different 1920x1080 images (in other words, double the number of addressable discrete pixels) and the projector's image processing engine blends them to smooth out stair-stepping and increase detail definition. The result, as far as the eye perceives, is substantially enhanced picture resolution compared to standard 1080p. Though the math says it is half the number of addressable pixels compared to native 4K, the eye will perceive most video material as much closer to native 4K than 1080p.
Physically the 4K DLP chip has 1/2 the number of mirrors. However, each mirror is used to define two discrete pixels on the screen by alternating its position in sequential refreshes. It is therefore able to address and display the full array of 3840x2160 pixels in the signal. If you look at a 1-pixel grid pattern projected by this 4K chip, you will see each alternating 1-pixel wide line cleanly defined as black and white. Conversely, with the pixel-shift technology used by JVC and Epson, this is not possible. Those machines use native 1920x1080 panels and offshift the pixel array diagonally on each alternating refresh. The maximum number of pixels they can address is 1/2 4K (or two times 1920x1080). Therefore a native 4K signal needs to be compressed to be displayed on these devices, where it does not on the 4K DLP chip. Though Epson and JVC's pixel shift technology is very successful in approximating native 4K video when viewed from typically viewing distances, it cannot reproduce a clean 1-pixel grid pattern like the 4K DLP chip can.