This is the nodal point for the fisheye lens mounted on the UR-E6 adapter at mode two (rectangular) fisheye. The right line is the nodal point. The distance between the lines is 21mm. Also the center tripod hole of the Nikon is where the 5000 camera case splits in half. You can see the split under the hot shoe, I finaly marked the split with the red arrow. So from the split to the first red line on the right is 94mm.