Here’s the set up: you fork over a king’s ransom for that new 1080p screen (projector, plasma, LCD, it doesn’t matter for this discussion). You place it in your home theater room, sit back, relax, and enjoy the fuits of your labor. But wait. There’s this nagging voice in the back of your mind that says “How come this doesn’t look better, or different than my old screen?” Let’s extend this question to, “Can I See the 1080p I just paid for?” The answer is a definite “maybe”.
If you are in your 20s, and have 20/20 vision, you can see better than most people in the world, and can see things as small as 1/60th of a degree of arc wide. What that means is, if your place a protractor at your pupil (figuratively!!!) and look at how wide 1 degree is, then divide by 60, that’s how small an object you can see. Anything smaller gets mushed into whatever is next to it and becomes indistinct. In order to see the pixels of a 1080p screen, they have to be at least 1/60 of a degree of your visionary arc wide. Simple math, right? It's all based on visual acuity. In fact, we don’t want to see pixels, so we want to sit just far enough away from our screen so as to have one 1080p pixel mush into the next creating a smooth pixel-free image. So just how far away is that? Here’s an example.
If you have a 42” 1080p plasma TV hanging on your wall, you’d need to sit at least 5.5 feet from it to blend those 1920 pixels into a smooth image. As you move farther, some that 1080p resolution is wasted. Any closer and you’ll see the dots. Again, that's assuming 20/20 vision. How many of you sit 5.5 feet from your TV? I didn’t think so. Most are more like 8 feet or farther. With your eagle eyes at 8 feet, the pixels mush together, even with the lowly 720p screen.
Let’s do the same calculations for a 50” screen. For a 1080p screen, plunk your chair at 6.5ft or more to just blur the pixels. At 720p, try a tad under 10 feet. Yes, 1080p is wasted on you for a 50” set at 10’. You just can’t see that well. And if you don’t have 20/20 vision (yea, me neither) these distances get shorter real fast.
Now, before we start getting all upset about how we think we can spot 720p over 1080i on broadcast TV stations, there’s a lot more at work than just the pixel count. We’re talking about display screens only here. Source material is a whole other discussion that includes the resolution of origination formats, how TV stations process images prior to air, bit rates, and much more. But broadcast HDTV is free to those with antennas, HDTVs are not. As a consumer, you owe it to yourself to know if spending more on your picture for higher than necessary resolution is smart, or just obsessive compulsive behavior. For smart consumers, we offer our consulting services to help you pick the perfect picture. For those with OCD, we recommend buying the highest resolution screen you can at any size and price. It’s probably cheaper than therapy.
Coming soon: How big a screen should you get?
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