Mitutoyo M plan Apo 20x NA 0.42
Some people regard the Mitutoyo M plan Apo’s to be the gold standard for photographing trough a microscope objective from 5x and up. As can be seen in the example pictures below the resolution is a little better than the Mitutoyo 10x but not very much.
Objective Mitutoyo M plan Apo
Magnification 20x
Numerical apperture (NA) 0.42
Resolution 0.65 µm
Depth of Field (DOF) 3 µm or 0.003 mm
Working distance (WD) 20 mm
Resolution r = λ / (2 * NA)
When the numerical apperture (NA) is 0.42 and the wavelength of light (λ) is asumed to be 0.550 µm (green light) the resolution (r) can be estimated to approximately 0.65µm;
r = 0.550µm / (2 * 0,42) ≈ 0.65µm
Depth of Field DOF = λ / NA^2
Depth of Field (DOF) is approximately 3µm or 0.003 mm;
DOF = 0.550µm / 0,42^2 ≈ 3µm or 0.003 mm
Disclosure: This is affiliate links. If you click through and make a purchase, I will earn a commission
Example photo below, butterfly scales from a Peacock butterfly or European peacock (Aglais io), Påfågelöga in Swedish. Mitutoyo M plan apo 20x, Raynox DCR-150 (208 mm) tube lens, Zerene Stacker, Adobe LR & PS. The second picture shows an enlargement just to show the detail you can photographed with this objectives with a 0.65 µm resolution. The stripes on the butterfly scales are quite visible, but not on all the scales. This is little better resolution than the Mitutoyo 10x.
Click and buy this picture at Alamy
