While most broadcast television shows and even local news remote units shoot in 1080p (typically with 24 or 30 frame per second refresh rates), the highest resolution high-definition broadcasts and prerecorded content is 1080i. But nearly all new displays are progressive, including our new friend 1080p. To convert interlaced video to a progressive format you must deinterlace it. Why is this important? Deinterlacing 1080i into 1080p creates a valid source of 1080p content.

Reassembly of those original progressively scanned frames isn’t all that difficult, at least on paper. The TV’s video processor takes the incoming signal and detects if the signal originally had a 24 or 30 frame sequence. It then takes the first and second fields (stored in memory), reassembles the progressive image, and outputs that frame. To keep the timing right the frame is output twice (and sometimes three times).  Even from this short discussion it should be clear that deinterlacing (reassembly) is tricky and is best avoided.

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Viewing Conditions
But even if you do have good, clean 1080p content, there is an optimal viewing distance for watching your new HDTV, and it’s probably closer than you’d think. The basic idea is to sit back enough so that the line structure (distance between pixels and scan lines) is not visible, but not so far as to not be able to resolve details in the image. The rule of thumb is to be 3,400 times the distance between the scan lines. This distance is easy to calculate. Let’s say you have a 50-inch TV that has a resolution of 1280 by 768 and the vertical height of the display is 24.5 inches. To get the viewing distance, divide the height (24.5-inches) by 768, and then multiply by 3,400. For this example we get a viewing distance of 108.8 inches. So, for that 50-inch, 768p resolution TV, we should sit about 9 feet away. Sit farther than that, though, and we won’t resolve the detail. Sit 9 feet away from the 1080p display and it won’t look any better than the 768p display.

 

One potential problem that occurs when you sit close to a bright TV is flicker. This is the physical perception of the actual flashing of the light source. Normally, TV images flash fast enough for us not to see the flicker. As the image gets brighter, like with newer technologies, our ability to see flicker increases. It turns out the peripheral vision is also more sensitive to flicker than the central vision area. So, if you rearrange your room so that you can sit 6.5 feet away from your new 50-inch 1080p panel, you will find that the screen covers a greater portion of your central and peripheral field of vision.