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Super-Takumar 105/2.8. Chipped and scratched front element.
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PostPosted: Sat Mar 23, 2019 12:39 pm    Post subject: Super-Takumar 105/2.8. Chipped and scratched front element. Reply with quote

I've shown this recent purchase on the usual thread, but I thought I'd provide something a bit more on how I'm trying to recover it.

The front element is heavily scratched and with three chips -



This is what it could produce as an example -


Wide open. Standard setting on Fujifilm X-E1, all parameters zeroed. No pp. Focal plane is on the acorns.



I took the lens apart and cleaned the optics, there was actually less crud in there than I expected, just the usual dust and particles that are dragged in over time. It was however, extremely difficult to take anything apart on it, some wrong-threading in the past, something that looked like dried lentil soup acting as a glue in places....


Once cleaned, I covered the front face of the front element in permanent marker felt tip, then buffed it back out. A lesson here is that it dried so fast, buffing was quite a laborious job. I think I need to put the marker in the fridge the next time to slow it's drying time down. The buffing left some of the deeper scratches and the chips filled. It's difficult to show, but here's two of the three chips I filled -

From front -


From rear -


And here's the same shot with the same settings (but a little more light I notice) after the clean up. Settings and focus as before. I've put a camera in so I can remember which one is which -




Comparison. Before.


After.





I spent an afternoon and night on this job. Was it worth it? Did I do the right thing? Can anyone see a difference?


I have to say that with only a few software tweaks, the image does become passable, but I've left it flat so I can judge progress.


It's my first time trying to resurrect a damaged optic. I'm basically at stage 1 I think, I've cleaned it and turned the chips to black dots. I'm sure there's much more (including doing a better blackening job on the scratches). I've not even tested flare yet.

Any advice or comment is very welcome, even if it is give up! The lens cost me peanuts. Thanks folks.


PostPosted: Sat Mar 23, 2019 5:27 pm    Post subject: Reply with quote

Like 1

The flare tests may reveal a better rotational position for front element to minimize effect. i.e., if a light upper right of frame causes problem, rotate lens element until effect is minimized, unless of course photos made with light upper right are rare.

Lighting difference between before and after photos makes spotting differences impossible for me.

Full frame camera may reveal more effect (s).


PostPosted: Sat Mar 23, 2019 6:07 pm    Post subject: Reply with quote

visualopsins wrote:
Like 1

The flare tests may reveal a better rotational position for front element to minimize effect. i.e., if a light upper right of frame causes problem, rotate lens element until effect is minimized, unless of course photos made with light upper right are rare.

Lighting difference between before and after photos makes spotting differences impossible for me.

Full frame camera may reveal more effect (s).



Excellent. That's exactly the type of thing I'd never think of. Rotating the element. Thank you.


On the lighting - yes, I'd agree. When it's overcast here ('before' shot), it's like living in a giant softbox. I waited and waited, but the sun didn't want to go in today. It's a busted comparison really.