Welcome to Nikonians! While Manual Focus AI and AIS lenses will mount on the D5000 and can be used in Manual (M) exposure mode the light meter built into the camera will not fuction with an AI or AIS lens mounted on the camera. You can set the correct exposure: 1. As George recommends using the Sunny 16 rule. 2. Using a hand held Lightmeter. 3. Using trial and error with the cameras Histogram. The only Nikon DSLR bodies capable of metering with MF AI or AIS lenses are the D_00 and D_ series bodies. These bodies will also allow using Shutter (S) priority exposure mode in addition to Manual (M) exposure mode. Good Luck and Enjoy your Nikons!