Here are the results of a more precise calibration for the entrance pupil of several lenses. The entrance pupil measurement L2 refers to the measurements listed in
Entrance Pupil Database - PanoTools.org Wiki This Database also lists appropriate dimensions of most cameras which will let you calculate the correct setting of these lenses on your camera.
P { margin-bottom: 0.08in; } Pentax DA* 16-50MM F2.8 @ 16 MM ~ 10.6cm is Nodal Ninja 5 Setting so 106.0-41.6 = 64.4mm is L2 for DA*16-50mm at 16mm
Pentax DA* 16-50MM F2.8 @20 MM ~ 10.3cm is Nodal Ninja 5 Setting so 103.0-41.6 = 61.4mm is L2 for DA*16-50mm at 20mm
Pentax DA* 16-50MM F2.8 @28 MM ~ 9.95cm is Nodal Ninja 5 Setting so 99.5-41.6 = 57.9mm is L2 for DA*16-50mm at 28mm
Pentax DA* 16-50MM F2.8 @35 MM ~ 9.10 cm is Nodal Ninja 5 Setting so 91.0-41.6 = 49.4mm is L2 for DA*16-50mm at 35mm
Pentax DA* 16-50MM F2.8 @50 MM ~ 8.10 cm is Nodal Ninja 5 Setting so 81.0-41.6 = 39.4mm is L2 for DA*16-50mm at 50mm
Pentax SMC 35mm f3.5 @35mm ~4.85 cm is Nodal Ninja 5 Setting so 48.5-41.6 = 6.9mm is L2 for SMC 35 f3.5
SMC 55mm F2 M42 @55mm ~4.25 cm is Nodal Ninja 5 Setting so 42.5-41.6 = 0.9mm is L2 for SMC 55mm F2 M42
Tokina EL 28mm @28mm ~5.65cm is Nodal Ninja 5 Setting so 56.5-41.6 = 14.9mm is L2 for Tokina EL 28mm K mount
Helios 44M-7 52mm F2 @ 52mm ~4.25cm is Nodal Ninja 5 Setting so 42.5-41.6 = 0.9 is L2 for Helios 44M-7 52mm F2 M42
Olympus Auto-T 85mm F2 @85mm ~3.8cm is Nodal Ninja 5 Setting so 38.0-41.6 = -3.6 is L2 for Olympus 85mm f2 with K mount
Please note - It was Difficult calibrating 85mm lens
These measurements are subjective - please let me know if you have different results from your testing.