Nikon 105mm f/2.8 Manual Focus Micro-Nikkor

The extension available is 31 mm, and the focal length at the close focus point is 91 mm.

Corrected focal length = Fc

    Magnification Subject distance Correcting Lens
Fc   Near focus Far focus Near focus   Far focus   Focal Length Diopters
                   
105 mm 0.49 0.00 10.83 in Inf in     0.00
95.02 mm 0.65 0.11 8.22 in 39.37 in 1000 mm 1.00
86.78 mm 0.81 0.21 6.62 in 19.69 in 500 mm 2.00
79.85 mm 0.97 0.32 5.55 in 13.12 in 333 mm 3.00
73.94 mm 1.12 0.42 4.77 in 9.84 in 250 mm 4.00
68.85 mm 1.28 0.53 4.19 in 7.87 in 200 mm 5.00
64.42 mm 1.44 0.63 3.73 in 6.56 in 167 mm 6.00
60.52 mm 1.59 0.74 3.36 in 5.62 in 143 mm 7.00
57.07 mm 1.75 0.84 3.06 in 4.92 in 125 mm 8.00
53.98 mm 1.91 0.95 2.81 in 4.37 in 111 mm 9.00
51.22 mm 2.06 1.05 2.59 in 3.94 in 100 mm 10.00
                     
33.87 mm 3.02 2.10 1.78 in 1.97 in 50 mm 20.00
26.25 mm 4.18 3.00 1.28 in 1.38 in 35 mm 28.57
22.11 mm 5.15 3.75 1.04 in 1.10 in 28 mm 35.71
                     
90.71 mm 0.73 0.16 7.34 in 26.25 in Nikon 3T   1.50
80.49 mm 0.95 0.30 5.64 in 13.58 in Nikon 4T   2.90
71.82 mm 1.18 0.46 4.52 in 8.95 in Both   4.40
65.26 mm 1.40 0.61 3.81 in 6.79 in 2 4Ts   5.80