Lens: Nikon El-Nikkor 75mm f/4
Vintage: Current.
Lens Mount: M39.
Needed Adapters: This lens can be used normally mounted or reverse mounted. To normally mount the lens you will need a M39 to your camera mount adapter, easily found on eBay. To reverse mount this lens you will need a reversing ring for your camera and a 40.5 to 52 mm step-up ring (52mm is what Nikon typically uses on reversing rings, yours may be different).
Preferred Mounting: Normal below 1:1, reversed above 1:1.
Filter Thread: 40.5 mm.
Street Price: Less than $100 in good used condition. Prices vary a lot online, shop around.
Controls: Aperture setting.
Aperture: 8 blades.
Basic Function: Requires a bellows to set focus and magnification
Normal Mount | ||
Extension | Magnification | Working Distance |
5 cm | 0.35 | 279 mm |
9 cm | 0.87 | 144 mm |
13 cm | 1.40 | 114 mm |
19 cm | 2.25 | 93 mm |
Est. Focal Length: 74.2 mm |
Reverse Mount | ||
Extension | Magnification | Working Distance |
5 cm | 0.51 | 208 mm |
9 cm | 1.03 | 133 mm |
13 cm | 1.56 | 104 mm |
19 cm | 2.38 | 91 mm |
Appearance:


Resolution vs. Aperture:
This lens is at its sharpest at f/8, both normally and reverse mounted. This lens has the most resolution at f/8 when normally mounted and at f/5.6 when reversed.
I would suggest using this lens at f/8 for the sharpness improvement although you could also go to f/5.6 when reversed although the improvement in resolution is small.
Corner Sharpness vs. Aperture:
The corner sharpness is very good at all apertures when normally mounted at a magnification below 1:1. when the lens is reversed, the corner sharpness is very good at f/8, as long as you are working above 1:1. Below 1:1 and reversed causes the corner sharpness to rapidly deteriorate.
This testing was performed at the minimum bellows extension for normal mounting and at 1:1 for reverse mounting.
Sharpness and Resolution vs. Magnification:
This lens shows good resolution and sharpness both normally mounted and reverse mounted. The curves are almost right on top of each other when used at the same magnification.
The corner sharpness is very good on a bellows. Below 1:1, normal mounting produces better corner sharpness and above 1:1, reverse mounting slightly outperforms normal mounting.
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.
The Nikon 75mm varies from very good sharpness to fair/poor at the high end of magnification.
A lens that performs in the fair/poor range doesn't mean that the lens is fair/poor, just that there are other lenses out there that will significantly out-perform that lens in that magnification range.
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.
The Nikon 75mm shows resolution performance that varies from very good at the low-end to fair at the high-end of its magnification range.
A lens that performs in the fair/poor range doesn't mean that the lens is fair/poor, just that there are other lenses out there that will significantly out-perform that lens in that magnification range.
Resolving Power vs. Magnification:
This graph represents the smallest details that are able to be resolved by this lens at various magnificaitons. If the number doesn't get smaller as the magnification rises, there is little benefit to going up in magnificaiton with this lens. This situation is also called empty magnification.
Good resolution, similar normal to reverse mounting. You can likely gain a little resolution by shooting at f/5.6 when reversed with a small loss in sharpness.
Chromatic Aberration:
This lens show mild color fringing in the center (about 0.20 - 0.50 pixel, nor and rev) and minimal/mild on the periphery (0.010 - 0.060%). Anything below 0.040% is not considered significant. Above 0.08% is considered moderately visible. Overall, lateral CA is best when mounted normally below 1:1 and mounted reversed above 1:1, similar to corner sharpness There is moderate axial CA on out-of focus details (see image below) as shown by a red fringe on the right and a green/cyan fringe on the left of the image.
Longitudinal CA:

Image Contrast: Image contrast is good.
Flare: This lens shows no significant flare during testing.
Distortion: This lens shows no significant distortion during testing.
Image Samples: Normal Mounting.
About 1:3 magnification, f/8, cropped and resized:

Pixel level crop from the image above:
There is very good pixel level detail, no problems.
About 1.8:1 magnification, f/8, stack of 9 images, resized:

Pixel level crop from the image above:
There is good pixel level detail, no problems.
Image Samples: Reverse Mounting.
About 1:2 magnification, f/8, cropped and resized:

Pixel level crop from the image above:
There is very good pixel level detail, no problems.
About 1.8:1 magnification, f/8, stack of 9 images, resized:

Pixel level crop from the image above:
There is good pixel level detail, no problems.
Conclusion:
This is an enlarging lens that performs well as a macro lens. It spans the range of magnification from about 1:3 to 2.5:1 on a typical bellows. As optics would suggest, it performs a little better when normally mounted below 1:1 and better when reverse mounted above 1:1 although the differences are pretty small in this case. This lens is easily available for a bargain price and is easy to adapt to a bellows.
The resolution and sharpness are good, but not quite up the standard of modern macro lenses. It has very good corner sharpness at f/8 and decent CA performance. Working distance is good and allows good lighting.
So, for the price, it is a good lens that can be a reasonable replacement for a modern macro lens across the typical macro magnification range and to well beyond 1:1.