It happens all of the time. Probably on most sessions or shoots that you go out on. You view through all of your images in your library or other viewer, and think to yourself, "hey something must be wrong with that lens. This does not look as sharp as it should."
Here's the thing. It is almost never the lens. It is almost always you...well, and me too. Camera shake or motion is the culprit. I know some of you have been doing this for a long time and certainly you know what you are doing. But consider that any small, even minute amount of motion from your camera or even mirror-shake can cause you problems that you will not see until you begin the edit. It will not show up on the back of your camera due to lower res nature of the preview.
There really is not anything you can do to be more certain of your image quality than to use a quality sturdy tripod. I know you've heard it before but it is true. Several years ago a few of us that were teaching at Brooks Institute of Photography in Santa Barbara, CA did some testing and the results were almost embarrassing. We were nowhere near as good as we thought we were in terms of hand-holding our cameras. The old rule we have all read about is true. Using the formula of a shutter speed that is a higher number, therefore faster than the focal length of the lens works as a terrific guideline. If you are using an 80-200 zoom lens your shutter speed has to be faster than 1/2ooth of a sec for maximum sharpness.
I know all about Canon's IS, Nikon's VR, and Tamron's VC systems of stabilizing for better hand-holding and they are all very helpful and are designed to allow you to hand hold at least two stops slower than without. Still, I recommend that you consider the original formula and try to stick to it. Oh and for the record, if you are working on a tripod, turn off your stabilization on the lens. It will not work properly when your camera is on a tripod and might actually make your images soft as it fights against the tripod.
For the past few years now I have been using a CLT104 model tripod from Induro. The head that I use on it is from Really Right Stuff and called the BH55. Terrific combination and all work together for maximum stability and low vibration. Couple the use of a tripod with the use of your cameras' mirror lock-up feature and you have an even more robust image quality.