Cameralabs.com skriver bl.a.:
The Nikon D5100 is the company’s latest ‘upper-entry-level’ DSLR aimed at beginners or those wanting a step-up from a basic budget model. Announced in April 2011, it comes exactly two years after its predecessor, the popular D5000. The new D5100 is positioned between the entry-level D3100 and the mid-range D7000, and goes head-to-head against Canon’s EOS 600D / Rebel T3i.
Externally the Nikon D5100 enjoys a redesigned shape that’s noticeably shorter than its predecessor and a little lighter too. Physically the biggest difference though concerns the screen round the back: it’s still articulated, but taking a leaf from Canon and Panasonic, it’s now hinged at the side rather than the bottom. Nikon’s also upgraded the screen from the basic 2.7in / 230k panel of the D5000 to a larger and much more detailed 3in / 921k panel here.