[experiment] Remove fungus damage by grinding the lens.

Latente · Joined: 12 Jan 2010 Posts: 17

So, i found a badly damaged canon serenar 50mm 1.8 for free
the 4 element is separated and the surface is damaged by fungus,
i try everything to clean it but the surface is compromised. so i thought, why don't try to grind it?
i have at home diamond paste from 0.5 to 15 (whatever it means) and plastic screech remover.

i try the finest paste and the screech remover but with like zero result.

did anyone tried to grind a lens?

RokkorDoctor · Joined: 27 Nov 2021 Posts: 1272 Location: Kent, UK

If the fungus damage is so deep that you need grinding rather than just polishing, I fear the lens may have been damaged beyond use. Grinding will affect surface curvature and element thickness, and will likely ruin the lens' IQ, especially if you don't have the right equipment.

For polishing you need the right polishing compound. Cerium oxide is the industry standard for optical polishing, not diamond paste. I assume diamond paste is too aggressive on glass and will leave too many scratch marks.

For polishing you will need to make your own polisher in order to maintain the correct surface curvature. This will be night impossible unless you are experienced in the making of polishers (making the base, applying pitch, setting the element into the pitch and removing the element without distorting the pitch, scoring the pitch, etc).

Once you have a correctly dimensioned polisher, polishing can be done by hand by very experienced craftsmen, but otherwise you would need to have a mechanical polishing set-up.

ZoneV · Expire: 2011-12-02

Yes, I tried this at least once on my Canon FD 300 mm f/2.8 L with some fungus traces in an inernal lens. It didn´t worke well, the fungus traces where still there. Back then I used cigarett ash or toothpaste.

Some years alter I used car glass polish for some other experiemnts, this works well!
http://www.4photos.de/camera-diy/Photo-Lens-Scratch-Repair.html
http://www.4photos.de/camera-diy/Lens-Coating-Removal.html

But as RokkorDoctor mentioned: You will destroy the original lens curvature! So the lens shape and performance is different afterwards. And the Anti reflective coating is removed as well, which could be a big problem.