Photo detail

Camera Maker Nikon Corporation Camera Model NIKON D90
Aperture f/3.8 Exposure Value 0 EV
Exposure Program Unknown: 0 Exposure Time 1/60 sec
Flash Flash, Auto-Mode, Return light detected Focal Length 24 mm
ISO 800 Metering Mode Pattern
Date/Time 2016:03:16 19:57:10 Resolution Unit Inch
X Resolution 240 dots per ResolutionUnit Y Resolution 240 dots per ResolutionUnit
Compression Jpeg Compression Contrast 0
Exposure Mode 0 Saturation 0
Scene Type Directly Photographed Sharpness 0
Subject Distance 1.41 Caption You can see the upper assembly after lifting off the base. The portion that rides on the outer bearing is just a flat surface with a taper to the middle. A lip around the edge minimizes dust infiltration.