As inaccurate as it is poorly written (and a sad commentary on
iStockphoto.com):

  The Truth About Resolution

Whenever an article proclaims "truth", baloney is sure to follow!

  When I became a pixel pusher years ago,

2?  3?

  one of the toughest concepts
  to wrap my brain around was that of image resolution:

And now she's an expert.  :)

  I know better now, but many professional designers don't. They buy a
  high-quality photo from a stock agency, open it in Photoshop, and
  black out with rage when they see "resolution = 72" in the Image Size
  dialog. An irate call to customer service usually ensues, followed by
  an embarrassing explanation of Resolution 101 by someone half their
  age. ...

Now we know how old she is.

  The Dark Art of Upsampling.

Be afraid, be very afraid!  :)

  The resolution measurement dictates how closely the pixels are packed
  together. Increasing an image's resolution means the pixels will be
  packed together more tightly, resulting in a smaller physical size,

Other way around, but who's keeping track.

  but generating a smoother, higher quality print. Lowering an image's
  resolution means loosening the pixels, resulting in a larger physical
  image size, but generating a blocky, lower quality print.

Sounds like slutty pixels to me!  :)

In fact any decent current printer driver does a good job of upsampling
before printing.

  Think of the resolution measurement as density. For example, the
  tighter a substance is packed, the denser it is and the less surface
  area it takes up (like brown sugar). The more loosely a substance is
  packed, the more surface area it consumes and it becomes less dense.

Are we talking crack or digital images?  :)

  Because our eyes can only process so much information, a 72 ppi image
  onscreen looks identical to a 600 ppi image onscreen. ...

Only if you have a crappy monitor or are legally blind.

  This gorgeous photo (courtesy of iStockphoto.com/Lisa Gagne) is
  measured at 72 ppi. Does that mean it's a low-quality image?
  Negatory, good buddy.

She's my buddy?  Does that mean what I think it does?  :)

  Evil upsampling method #1: Open the Image Size dialog in Photoshop,
  take a deep breath, and leave the Resample Image box checked. (I
  realize I just told you not to do this, but bear with me.) Choose
  Bicubic Smoother from the pop-up menu to its right and change the
  document dimension pop-up menus to Percent. Enter 110% in the width
  box and press OK (Figure 3). Repeat this process as many times as
  necessary to enlarge the image. For some reason, adding data 10% at a
  time doesn't cause a huge amount of quality loss. Do resist the urge
  to increase the size more than 10% at a time, unless you want that
  chunky look.

Stairstep interpolation is actually a bad idea.  Bicubic Smoother works
best in a single step.

  Evil upsampling method #2: Buy a plug-in, such as Genuine Fractals by
  onOne Software, Blow Up by Alien Skin, or PhotoZoom Pro 2 by
  BenVista. They pull off some serious voodoo and somehow manage to
  increase pixel data without totally destroying the image.

As my own tests show ("Adobe Bicubic Smoother upsize vs Genuine
Fractals"), there is very little difference between Bicubic Smoother and
Genuine Fractals in large upsizing, and none at all in modest upsizing.

  I Wouldn't Lie to You

When someone says "I Wouldn't Lie to You" you can be sure they're about
to lie to you.  Think used car salesperson.  :)

  Resolution doesn't mean squat until that image is headed for a
  printer. ...

And not even then, since the printer driver will upsample for you.

  Lesa Snider King is the chief evangelist of iStockphoto.com and
  founder of GraphicReporter.com.

Yet she doesn't know how printer drivers work, thinks stairstep
interpolation works, and doesn't know how well bicubic smoother works.
Yikes!

I didn't think much of the article.  When I first found rpd many years
ago I got on a soapbox about resolution and didn't change very many
minds.

Problem is, there are MANY definitions of resolution.  There is no
final arbiter of English language.

However, to my mind the best definition of resolution is what film
photography used to use- an actual MEASURED value based on test
charts.

To me the number of pixels in the image is just that- a number!
Theoretically there is a ratio of the resolution in each direction to
the number of pixels in that direction. In a PERFECT camera with a
perfect lens, the actual measured resolution would approach that
number (about 0.7 times the number of pixels).  But of course, no
camera and no lens is perfect.