The Nikon 28mm f/1.8G has a rearward focus shift, which can be characterized as “substantial”.
For precision work where one desires full sensor resolution from a high-res digital camera, focus shift is a sharpness-robbing problem for high resolution digital.
Focus shift is a confusing topic, and one which interacts with the varied precision of the autofocus system to further confuse the issue.
Focus shift and how to deal with it are discussed in Making Sharp Images. A brief discussion follows the images.
Article continues for subscribers...
diglloyd Advanced Photography includes hundreds of pages of exclusive coverage and high resolution, Retina-grade example pictures detailing Canon and Nikon DSLR bodies and their lenses, with in-depth analysis of sharpness and contrast, color, bokeh, vignetting, distortion, MTF, and flare. Also included is a wealth of in-context technique and workflow insight. Since 2006, diglloyd Advanced Photography is the authoritative review and on-line reference for discerning Canon and Nikon shooters. Subscriptions cost $ per year.