Instructor Insights: Editing on LCD monitors:

We're not talking about the monitor on your desk - we're talking about the one on your camera.

"One lesson that's important to learn in a situation like this is that the LCD monitor on your digital camera is too small to really ascertain whether or not you have critically focused on a subject. The detail just isn't there. Therefore, just keep shooting and edit the pictures later. LCD monitors are great for checking compositions and exposure, but you can't know if your images are tack sharp or not even with the ability to magnify them. You may be able to tell if they are definitely out of focus, but you can't know if they are tack sharp. "

One of the important abilities in digital photography is the ability to check your work immediately after shooting. You can check your composition, your lighting, make sure there are no distracting background details, even see if your shot is woefully out of focus. What Jim's telling us in the linked article is that you can't tell the difference between something which is pretty-much focused, and something which is perfectly in focus. For that, you need to wait until you get home and get the images off your camera.