5. AF Fine-TuningCameras and lenses are precision instruments. Even so, there's a chance that a given lens might be "out of sync" with a given camera body. Many of today's DSLRs allow you to compensate for this by shooting a series of test shots using the camera's AF-tuning feature to adjust focus closer to and farther from the camera in fine increments. You then examine the resulting images on your computer monitor, pick the sharpest one, and set the camera accordingly. The camera will thereafter apply that correction each time you use that lens. You can store corrections for a number of lenses, which varies per camera model. Canon calls this feature AF Microadjustment, Nikon calls it AF Fine Tuning, Olympus calls it AF Focus Adjust, Pentax calls it AF Adjustment, and Sony calls it AF Micro Adjustment.
6. Improved High-ISO Image QualityMost of today's DSLRs produce amazingly good image quality at ISO settings of 800 and even 1600, with some going as high as 6400 with good results. (Settings above 6400 are best left for low-light emergencies, especially with smaller-sensor cameras.) Considering that ISO 800 was about the limit for good results with film, that's truly remarkable. Lots of new technology makes this high-ISO performance possible, including better sensors, smarter image processors and processing algorithms, and more sophisticated noise-reduction systems.
Nikon has been a leader in high-ISO equivalents. The new Nikon D3S, which has a normal ISO range of 200-12,800, offers an expanded range all the way up to an astounding ISO 102,400! Right behind the D3S came Canon's EOS-1D Mark IV, which also offers a maximum ISO of 102,400. These are really game-changing numbers and even more impressive when you consider how far the technology has come in a short time.
That said, all digital cameras still produce their best image quality at lower ISOs, generally the lowest setting in their "normal" ISO range. "Expanded" ISO settings, whether higher or lower than the normal range, result in reduced image quality, so stay in the "normal" range for best image quality and at the lower end of that range unless the situation really requires a higher ISO setting.