If you've wandered into the television section of your local
electronics shop lately, you've seen sets sporting something
called "4K."  The feature designates a new, super-high
resolution picture standard. Retailers have created special
displays to tout such sets, and a growing number of models
you'll see in their showrooms have the feature built-in.  4K
sets, which have four times the number of pixels as regular
high-definition ones, have actually been available for more than
a year now. But they've plunged in price over the past six
months or so. While you used to have to pay thousands of dollars
extra for a 4K set, you can now find some at smaller screen
sizes that are comparable in price to the top-of-the-line non-4K
models.  But if you're thinking it's time to rush out and buy a
4K TV, take a moment to catch you breath first. Here are some
things to consider:  Size matters -- a lot. The ability to
perceive all the extra visual information in 4K pictures is a
function largely of viewing distance and the s