Can I remove and clean haze or fungus on the rear element of a Zeiss Planar 50mm f/1.7 without affecting focus calibration?
Asked 1/14/2018
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I bought a Zeiss Planar 50mm f/1.7 with faint haze/fungus visible on the rear element. The retaining ring around the rear glass appears to have two spanner notches, so it looks like the rear element might be removable from the back.
Before I try, I want to know:
- Is the rear element on this lens likely to be accessible by removing that rear ring?
- If I disassemble it from the rear, is there a risk of disturbing optical alignment or focus calibration?
- Is there a reason some repair guides start from the front instead?
- For now, what is safe to use on the outside of the lens: blower, brush, LensPen, microfiber cloth, etc.?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
1
I looked into this and it does appear the only want to know for sure is to try unscrewing the rear lens ring to see if it gives you access to the rear element. My belief is that it will. However, no matter how careful you are, you would likely need a collimator in order to reassemble the element and ensure that it is in proper alignment. My estimation is that the rear ring is set to ensure proper distance from the film plane for the rear element, and that is a likely reason that repair videos recommend disassembling from the front.
In the meantime, you should have no issue using a brush to remove dust and a microfiber cloth to keep the external surfaces of the front and rear element clean. I prefer to use a bit of hot breath with the microfiber unless there is more stubborn dirt or oil, which may require a small bit of lens cleaner applied to the cloth (not directly to the lens).
Originally by user26639. Source · Licensed CC BY-SA 4.0
user26639
7y ago
0
Generated from our catalog & community — verify before relying on it.
It may be physically possible to remove the rear retaining ring with a lens spanner and access the rear element, but the bigger concern is reassembly accuracy. On lenses like this, that rear ring may help set the rear element’s spacing and alignment relative to the film/sensor plane. If you disturb it, you can affect collimation and performance, and proper reassembly may require a collimator or other service equipment.
That’s a likely reason many repair procedures start from the front instead of the rear.
So: yes, the rear element may be accessible, but it is not risk-free. If image quality and correct focus matter, professional service is the safer option.
For routine exterior cleaning only, a blower or soft brush is fine for dust, and a clean microfiber cloth is suitable for the outside surfaces of the front and rear elements. Light moisture from breath can help with minor smudges. Avoid aggressive cleaning or using tools meant for external surfaces to try to remove anything inside the lens.
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AI8y ago
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