Lens: Nikon 5x measuring objective
Vintage: 1980's - 90's?
Lens Mount: M26.
Needed Adapters: I have a M26 to 52 mm male thread. A 55-52 mm step down ring can be used as a 52 mm female to female adapter. That will connect to a 52 mm reversing ring.
Preferred Mounting: Normal, not reversed.
Filter Thread: None.
Street Price: $250 - $500 in good used condition. Prices vary a lot online, shop around.
Controls: None.
Aperture: Fixed aperture - NA about 0.10 by my measurements.
Basic Function: Requires a bellows to set focus and magnification.
Extension | Magnification | Working Distance |
5 cm | 2.86 | 70 mm |
9 cm | 3.81 | 67 mm |
13.8 cm | 4.98 | 65 mm |
16 cm | 5.49 | 63 mm |
19 cm | 6.18 | 62 mm |
Est. Focal Length: 42.4 mm |
Appearance:


Performance: Sharpness vs. Magnification:
I have 4 lines that represent levels of performance from outstanding (top) to fair (bottom). This shows where this lens fits into the hierarchy that I have created.
This lens shows very good to outstanding sharpness across most of its magnification range, being good/very good at the highest magnification.
Performance: Resolution vs. Magnification:
I have 4 lines that represent levels of performance from outstanding (top) to fair (bottom). This shows where this lens fits into the hierarchy that I have created.
This lens shows very good resolution across the lower magnification range and good resolution at the highest magnification.
Corner Fuzziness vs. Magnification:
this lens shows good corner sharpness at the lowest magnification, improving to very good at higher magnifications.
Resolving Power vs. Magnification:
This graph represents the smallest details that are able to be resolved by this lens at various magnifications. If the number doesn't get smaller as the magnification rises, there is little benefit to going up in magnification with this lens. This situation is also called empty magnification.
No problems although the resolution improvement above 5:1 is pretty minimal.
Chromatic Aberration:
This lens show mild to moderate color fringing in the center (about 0.45 - 1.72 pixel) and moderate/severe on the periphery (0.126 - 0.238%). Anything below 0.04% is not considered significant. Above 0.08% is considered moderately visible.
There is moderate axial CA on out-of focus details (see image below) as shown by a purple fringe on the right and a green fringe on the left of the image.
Longitudinal CA:

Image Contrast: Image contrast is very good, typical for a high-quality objective.
Flare: This lens shows no significant flare during testing.
Distortion: This lens shows no significant distortion during testing.
Image Samples:
About 2.8:1 magnification, focus stack of 43 images, resized:

Pixel level crop from the image above:
There is very good pixel level detail, no problems.
Pixel level crop from the corner:
There is slight fuzziness in the corners, not bad.
About 5:1 magnification,, stack of 34 images, resized:

Pixel level crop from the image above:
There is good pixel level detail, but getting slightly fuzzy.
Pixel level crop from the corner:
There is slight fuzziness in the corners, not bad.
Conclusion:
This is a fairly commonly seen objective that can be purchased for a reasonable amount of money used. It is fairly easy to adapt to a bellows as it has a standard M26 microscope mount. It has very good resolution and sharpness and outstanding working distance for the magnification. It also has very good image contrast. Corner sharpness is generally very good. About the only weak spot is that is has quite a bit of chromatic aberration - not really all that bad since most objectives have the same problem. It also has some moderate vignetting in the corners at the lowest magnification (darkening of the corners), but that clears up once it reaches its intended magnification of 5:1. The vignetting is easy to see with my test slide, but not particularly visible with real images, so not a big problem unless you are shooting against a bright, homogeneous background.
All-in-all it is a good objective with performance similar to other objectives of similar NA, except for its outstanding working distance. My 4x phase objective has a WD of about 14 mm at 5:1 while this has a WD of 65 mm at the same magnification. That working distance makes lighting things much easier.
Additional Note: By my own observations, this lens appears to be telecentric at 5:1. I figured that it might be since it appears to be made for measurements. Telecentricity is a lens design trick that means that there is no change (or at least very, very little) in perspective (parallax) as you move across the field of view of the lens. An example of this feature would be: If a tree is between you and a man, you can't see the man from straight on, but if you move to the side, the tree will move out of the way and you can now see the man. With a telecentric lens, the man will be behind the tree no matter how you move, there is no parallax. Telecentric lenses are used for measurements because an object that is 1 inch will project onto the detector as the same size whether it is 6 inchs or a foot away. An inch is an inch. Another way to look at is that the field of view of the lens is a cylinder extending out from the lens. The field of view doesn't get bigger as you move out from the lens. An offshoot of this is that the field of view can be no larger than the lens itself, so it's only really useful with fairly close-up imaging.
Telecentric lenses can be useful for stictching images together to make a "panoramic" image. A complex 3D object will appear the same whether on the right or the left of an image and the images will knit together more cleanly as a result.