Lens aberrations can be problematic, but using the sweet spot of your lens isn't the only solution. Many RAW conversion programs contain information about the most popular lenses, which allow the program to correct for chromatic aberrations and vignetting automatically—although there's nothing they can do about the softness caused by spherical aberrations or diffraction (see Figure 13).
Figure 13 The Lens Corrections pane in Lightroom 3 corrects chromatic aberrations, vignetting, and optical distortion. The sliders let you adjust the strength of the corrections.
Your camera may also have menu settings to negate the effects of some aberrations. The newest Canon EOS cameras, for example, have a Peripheral Illumination Control function that eliminates the dark edges caused by vignetting (see Figure 14). The EOS 1Dx also has in-camera correction for chromatic aberration. You should check your camera's instruction manual to see whether it has similar functions.
Figure 14 The Peripheral Illumination Correction function on the EOS 5D Mark II corrects vignetting for Canon lenses used with the camera.