The problem is audio. The left and right front speakers are farther apart than they should be, giving you a too-wide sound stage.
So how do you calculate the proper distance?
You can do it with Bale’s spreadsheet. Change the number in cell C11 to 3840 and cell C12 to 2160. (Check your television’s specs: A few 4K sets actually deliver 4K resolution: 4096 x 2160 pixels.)
Another way to look at it is to consider your field of vision rather than the distance to the couch. For a 1080p TV, THX recommends that the screen take up no more than 40 degrees of your field of view. For 4K sets, THX increases that to 60 degrees.
A digital image is made up of thousands of dots called pixels (short for "picture elements").
At this point, you’re probably wondering about the math. How do you figure out that the horizontal width of the rectangle in front of you doesn’t take up more than a 6th of a full circle?
That’s a lot more complex than measuring the distance between a TV and a chair. Here’s how to do it: First, multiply the advertised, diagonal size of the 4K TV by 0.87. That formula tells you that a 50-inch set is 43.5 inches wide.
Next, visit the Angular Size Calculator. Click the Distance button. Enter 60 for the angle (I’m assuming a 4K TV here). In the Size field, enter the width you calculated above.
The result will be the closest desirable distance in inches. For a 50-inch TV, that’s just a bit over three feet. That’s still awfully close.
When the resolution changes
Your TV has a fixed resolution, either 1080p or 4K. But the content you watch will vary considerably. Most Blu-rays are 1080p (the “p” indicates progressive scanning). All DVDs are 480p. Broadcast TV could be 480i (the “i” interlaced interlaced scanning), 480p, 720p, or 1080i. Streaming content? Who knows. It can change in the middle of a program, based on your broadband speed.
When most TVs receive a lower-resolution signal, they'll will upscale it to the television’s native resolution—unless your DVR, cable box, Roku, or other device does it first.
But there’s something you need to understand about upscaling: It doesn’t improve the picture. Sure, technically, the TV is displaying its full resolution. But a 480i signal upscaled to 4K still contains only 480i worth of image information.
So if you place your chair close enough to become immersed in 4K splendor, many of the programs you watch will look pretty bad. You probably won’t see actual pixels—the upscaling algorithms manage to hide that—but you’ll get blurry images.
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