Lens: Minolta 50mm f/3.5 Rokkor-X auto bellows
Vintage: Uncertain.
Lens Mount: Minolta MD mount.
Needed Adapters: This was a tough lens to adapt to a Nikon mount. My inital though was to get a cheap 5-piece extension tube set off of eBay and since these are modular, I could screw the Nikon male portion onto the Minolta female portion (This works well for many lens mounts). When I bought a Minolta version of the extension tubes, I found that the threads were reversed and the male Nikon portion and the female Minolta portion have the same threads. I then found a 57-58mm step-up ring and screwed that into the Minolta side. Then you get a 58-52 mm step down ring and then that can be screwed into a reversing adapter. Not the easiest adapter, but it works.
Preferred Mounting: Normal, not reversed
Filter Thread: 34 mm on the lens. Has a screw-on lens hood that is 55 mm.
Street Price: $150-$200 in good used condition. Prices vary a lot online, shop around.
Controls: Aperture setting
Aperture: 6 blades
Basic Function: Requires a bellows to set focus and magnification
| Extension | Magnification | Working Distance |
| adapters | 0.45 | 146 mm |
| 25 mm | 1.01 | 86 mm |
| 5 cm | 1.31 | 71 mm |
| 9 cm | 2.09 | 57 mm |
| 13 cm | 2.88 | 49 mm |
| 19 cm | 4.04 | 44 mm |
| Est. Focal Length: 51.2 mm | ||
Appearance:
Resolution vs. Aperture:
The sharpest aperture is f/8 and the most resolving aperture is f/6.7. There is a good argument for using f/6.7 since the sharpness is very nearly the same as F/8 and the resolution is superior. The only problem with that is a loss in depth of field at f/6.7. I would suggest that f/8 is adequate at lower magnification and f/6.7 is good for higher magnification.
Corner Sharpness vs. Aperture:
The corner performance of this lens is extremely good, even at large apertures. The interesting part is that the corners outperform the center at larger aperture - i.e. The corners are sharper than the center. This results in negative corner sharpness numbers. i haven't seen this before with a lens.
At smaller apertures, the lens shows virtually the same sharpness and resolution in the far corners compared to the center. Overall the best corner performance that I have com across to date.
(Testing done at 1.31:1 magnification. Numbers at each aperture setting will tend to improve as the magnification is increased and worsen as the magnification is decreased.)
Sharpness and Resolution vs. Magnification:
This lens shows good sharpness and resolution across its usable magnification range of 0.5x - 4x. Compared to similar 50 mm lenses such as the nikon El-Nikkor 50mm f/2.8 and the Nikon 50mm f/1.8 reversed, it has less resolution and sharpness although the difference is pretty small. It significantly outperforms these lenses in the corners.
If you want corner to corner sharpness, this is a very good lens.
You will notice that the corner performance starts to suffer at a magnification of 0.50:1. This magnification is achieved when the lens is mounted directly on the camera body. I think that 0.50:1 is starting to get out of the design range of this lens. It works best at 1:1 and above.
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 Minolta 50mm shows sharpness that varies from very good on the low-end of magnification to fair/poor on the high-end.
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 Minolta 50mm shows resolution varying from very good at low magnification to poor at the high-end. Its resolution performance is hampered by having f/8 as its sharpest aperture. This could be improved a little by shooting at f/6.7 at high magnification.
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. You could likely squeeze a little more out of this lens by shooting at f/6.7 with a slight drop in sharpness.
Chromatic Aberration: This lens show minimal color fringing in the center (about 0.30 - 0.80 pixel) and even better on the periphery (0.05 - 0.80 pixels). Anything below 1.0 pixel is good.
Image Contrast: Image contrast is good across the magnification range.
Flare: This lens shows no significant flare during testing.
Distortion: This lens shows no significant distortion during testing.
Image Samples:
About 1:1 magnification, f/8, resized:
Pixel level crop from the image above:
There is good pixel level detail, no problems.
About 2.9:1 magnification, f/8, stack of 22 images, resized:
Pixel level crop from the image above:
Again, good detail, no problems. A little light leakage from the outside window in the room can be seen on the left edges of the relief. This can be sured by placing a dark sheet next to the copystand to block that light.
Conclusion:
This is an unusual and hard to find lens. I have only ever seen two of them, and I own one. Across all brands, there are very few bellows lenses in the 50 mm range. Not sure on the reasoning behind this.
This lens has good resolution and sharpness, but it does get slightly outperformed by other lenses in its focal length range. This is probably related to having f/8 as the sharpest aperture. Most lenses that I have tested in this focal length range are sharpest in the f/4 to f/5.6 range.
Where this lens shines is in its corner performance. There is virtually no loss in resolution or sharpness even in the extreme corners of the frame. This combined with an almost total lack of distortion suggests that this lens should be very good if you plan on stitching images together (doing micro panoramas).
I would suggest that its usable range is really from 1:1 to 4:1 and that means either using a little extension or a bellows. Mounting it straight onto the camera is OK, but the corner performance suffers a bit.