The D40, D40X, D60, D3000, D5000, D3100, and D5100 bodies do not have AF motors built into the camera body and require AF-S type lenses that have the AF motor built into the lens to provide AF. The D200 has an AF motor built into the camera body that drives the screwdriver type AF mechanism in the AF 50mm f/1.8D. While the D200 will provide metering with your 50mm f/1.2 AIS, the D40 will not. Though it will mount on the D40 and work in Manual mode using the Sunny 16 rule or the histogram via trial and error to set the exposure. Good Luck and Enjoy your Nikons!