"NASA/JSC has a requirement for multiple digital cameras and camera peripherals. The digital cameras and all camera peripherals must be manufactured from the same lot. NASA has a requirement for 48 Nikon D2XS SLR Digital Cameras. The cameras must be lubricated with Braycote lubricating grease which is approved for spaceflight during the manufacturing process. Attempts to compete similar efforts have been unsuccessful due to the camera equipment having to be manufactured from the same lot and items requiring Braycote lubricant grease having to be lubricated during the manufacturing and assembly process."
Editor's note: This Expedition 15 photo should give you an idea of what camera gear they already have on orbit.