4. Fast Enough

As far as autofocus is concerned, both cameras offer a choice between AF-S (Single AF) and AF-C (Continuous AF). The latter is naturally the one to use on moving subjects. Nikon adds an AF-A mode where the camera automatically chooses the appropriate mode, but that function didn't really impress us. In practice, both models provided good focusing in most situations, with the Nikon being a little faster and also a little more efficient in very low light. The D50 has a lighting system for shooting when there's almost no light, but we found it somewhat unpleasant and intrusive for the subjects being photographed. In practice, you can almost always do without it, and disabling it seems to us like a good idea.

The overall score here, then, is in favor of Nikon, but with one advantage for Pentax: The autofocus system they use lets you readjust the focus, since the lens "unlocks" once you've focused. On the other hand, Pentax doesn't offer a system like that used for Nikon's AF-S - a motor built into the lens that makes for much quicker focusing. Admittedly, though, few purchasers of a DSLR like the D50 will be buying lenses of this type, which are generally very expensive. Naturally, manual focusing with electronic assistance (illumination of the focus indicator) is possible on both cameras.

On the istDL, a depth-of-field preview lets you see the actual appearance of the image before you shoot. You simply pull the tip of the main switch to the right to stop down the diaphragm. On the Nikon, this function has disappeared - it existed on the D70 - and that's regrettable; even if the feature wasn't essential, It's useful.