The teacher in me often wonders about online learning here's an example that comes close, it's an introduction to the Canon 300/350d and a general introduction to digital photography, on the surface a little simplistic, but probably more engaging than actually reading a manual.
The image on page 8 section 10 which is the section that looks at factors affecting sharpness has some flare in in the top right corner, probably because the photographer didn't buy the most important and cheapest of accessories, a lens hood. I also disagree with the low contrast versus high contrast lighting situations argument. A good lens produces a sharp image regardless of lighting [assuming you expose correctly and have the camera on a high enough shutter speed to avoid camera shake].
To quote on of my mentors and friends,
The photographic process looks after itself when its natural inheritance is honoured. It can not understand any other way of working. But when what is passed on represents a loss, the process collapses.††Les Walkling
In essence every part of the process has the capability to multiply errors made to the point where the image loses all meaning and coherence. So buy a lens hood, use a tripod if you expect to work in light conditions and small apertures that require a shutter speed lower than the focal length of your lens. For example, my Hasselblad has an 80mm lens, I never handhold under 1/125, [the next shutter speed is 1/60 lower then 80] of a second, when using a 35mm camera if I had a zoom on it, that went from 80-200, the lowest handheld shutter speed I could use would be 1/250th.
Ultimately though it comes down to your own expectations and appreciation of what constitutes a sharp photo and what is more important to you. Look at the masters, look long hard and often, however, never forget to let go in a Zen kind of way, and free you mind up while working.