Can spacer rings correct softness after replacing the front element in a Nikon 35-70mm f/2.8?
Asked 7/3/2020
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I replaced the scratched front element in my Nikon 35-70mm f/2.8 with a front element from another old lens. The lens still works, but it is now slightly soft at the long end. I noticed spacer rings inside the lens and want to know what they do. Can changing or adding/removing these spacer rings be used to restore sharpness or correct the softness after a front-element swap?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
1
It does not seem possible to use the spacer rings to adjust the lens at the long end. There are only two sets of spacer rings in the lens, one set behind the first lens group, and one set in front of the lens mount.
The first set of spacer rings can be seen in the figure above marked with 1K160-756 to 760. It is not very easy to read, but it is the 8th item from the top left. In the figure below it is marked with number 94, the 3rd number from the top left. The second set of spacers is marked with 1K161-160 to 168 (or 178) in the figure above,and it is the 4th item from the bottom left. It is marked with 97 in the figure below, and is the 5th number from the bottom right. Item 1K161-178 is also marked as 97 below, but I haven't found it in the figure above yet. Under the pictures is a copy of the page from the parts list where they are listed.
Here are some links that I found very useful on how to clean/repair this lens:
Mikeno62 at Youtube. Please give this guy a thumbs up if you like the video, I think it is very well deserved.
https://www.youtube.com/watch?v=o6dB0cCzYBE&t=1191s
DIY extravaganza on Youtube, also great work:
https://www.youtube.com/watch?v=0v2XZHtkLVQ&t=631s
Originally by user40887. Source · Licensed CC BY-SA 4.0
user40887
6y ago
0
Generated from our catalog & community — verify before relying on it.
Spacer rings in a lens set the precise spacing between optical groups. That spacing is part of the optical design, so changing it alters lens performance rather than serving as a simple sharpness adjustment.
Based on the answers, the spacer sets in this lens are not intended as an easy way to tune softness at the long end. More importantly, swapping in a front element from a different lens is very likely the real cause of the softness. In complex lenses, even the air gaps between elements matter optically, and substituting a non-matching element can degrade image quality.
The scratches on the original front element probably had little effect compared with using the wrong replacement element. So the practical answer is: don’t try to fix this by guessing at spacer thickness. The correct remedy is to reinstall the proper matching front element or have the lens professionally serviced and collimated.
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UniqueBot
AI6y ago
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