What’s really important: Sensor size. A bigger light sensor in the camera means better light sensitivity, which means the shutter doesn’t have to stay open as long, which means fewer blurred shots.

But the camera companies don’t want you to know this statistic  it’s not on the box, it’s not in the ads  because it’s easier and cheaper to goose the megapixels than the sensor size. You can look up a camera’s sensor size on the Web, but even then you’ll be presented with goofy, hard-to-understand, impossible-to-compare measurements like 1/2.3 inches (for small cameras) and 16 x 23 mm (for S.L.R. cameras). They never, ever appear in simple diagonal inch measurements, the way TV screens (and even camera screens) are measured. No, that would be too simple.

Cellphones What you’re told is important: coverage. What’s really important: coverage.

Yes, they’re advertising the right thing. Coverage is what people want. We don’t want to see no bars and be unable to make a call; we don’t want interrupted conversations when we go through dead spots. We just want the darned thing to work.

The real problem is that they’re lying. The first clue is that, despite all of those claims, we still complain about our cellphones’ coverage.

The second clue is that every cellphone company makes a similar claim. “More bars in more places” ... “Largest network” ... “Most reliable network” ... “Fewer dropped calls.” They can’t all be right. (Turns out they’re measuring different things  how many people live within the coverage area, for example, versus how many square miles are in the coverage area, or coverage in the United States versus worldwide coverage.)

The third clue is the coverage maps on each company’s Web site. Zoom in a tad, and you find out that lots of states have more dead spots than live ones. I’d sure hate to be a cowboy trying to make phone calls while galloping through Wyoming, Montana, Idaho, Arizona and Nevada.

It’s not easy being a cellphone company, of course. It’s expensive to put up cell towers, and it’s not worth doing in sparsely populated areas. And even in populated areas, you have to fight the locals who don’t want big ugly towers in their backyards.