So you’ve used your entry-level consumer DSLR avidly for a few years and want to take your picture popping pastime one step further. You don’t have the budget for a proper professional camera, but you’d still like something a little speedier and a bit more robust than your current model. Nikon’s solution: The $899.99 D5100. The successor to the Japanese company’s popular D5000, this new camera offers significant upgrades that range from improved image quality to enhanced functionality.