>Anyway, here is an example in my Flickr account that baffles >me, and surely takes my into the realm of fear as to >determining a method of checking softness on my own. > >http://www.flickr.com/photos/91580196@N06/8348071046/in/photostream > >There are so many menu screens in a D7000, I am intimidated. I >have a hard time remembering not to use f1.8. LOL
I've never heard of an f/1.8 105mm lens. I think you mean f/2.8.
If the sample photo was shot at f/2.8, then your depth of field (DoF) was simply too shallow to include the entire spark plug. Try f/5.6 and reshoot the plug. Compare the two shots to see the difference when using a larger aperture (f/2.8) compared to a somewhat smaller aperture (f/5.6). If the plug still isn't fully in focus at f/5.6, reduce the aperture to f/6.3, and re-compare.
Knowing the fundamentals of aperture size (f/stop), shutter speed, ISO and white balance, as well as practicing good handheld and/or tripod technique, and experimenting with the autofocus system to gain a good feel for its nuances, will help you make better and better exposure decisions more often as time goes by.
There's nothing wrong with your camera or your lens or your subject matter.