Home
SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Super-Takumar 105/2.8. Chipped and scratched front element.
View previous topic :: View next topic  


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.


PostPosted: Fri Mar 29, 2019 12:38 am    Post subject: Reply with quote

A freind of mine once tried johnson wax on CD's of a video game that was no longer available. Then buffed until it looked clear . It worked. It would be reversible (it would come off with a an organic solvent like acetone). Might be worth a try.


PostPosted: Wed Apr 10, 2019 6:38 am    Post subject: Reply with quote

jamaeolus wrote:
A freind of mine once tried johnson wax on CD's of a video game that was no longer available. Then buffed until it looked clear . It worked. It would be reversible (it would come off with a an organic solvent like acetone). Might be worth a try.



Thanks Jamaeolus. Is that the floor wax?


PostPosted: Wed Apr 10, 2019 6:51 am    Post subject: Reply with quote

To give me time to discover the miracle cure for overzealous lens cleaning, I've ordered a lens hood from China that should allow the angle of view (on apsc) without vignetting it, but no more than that. My calcs say it will be tight, so I hope it's on the wide side of tight.

And while stripping out the glass for cleaning, I came across a screw without a home. Mmm... interesting I thought, I can't see where it goes, it doesn't look like the others and it doesn't seem to be hurting the operation of the lens. I wonder if it just fell in some time in the past 50 years. Well, nope, since closing the lens back up and finally beginning to use it, I now have an ever loosening barrel with a 'clunk' when you begin to turn. ! I suspect there's a connection. Any ideas on that one would be appreciated before I go back in.

This lens is turning into a challenge
Smile .


So where do you belong fella!?


PostPosted: Wed Apr 10, 2019 9:25 am    Post subject: Reply with quote

Sciolist wrote:
I now have an ever loosening barrel with a 'clunk' when you begin to turn. !

If we assume this is not due a poor connection with the adapter, which causes the impression,
this to me sounds like it most likely coming from either of the two places.

First is the mount of the internal tab, which prevents inner barrel from rotating when you focus.
In most lenses there are two bolts holding the tab, and loosing one will result in a wobble and potential clicking noises when turning focus ring.
Second place would be bolts engaging focus ring to helicoid, but I'm fairly sure you need to lose more than one bolt there to make it wobble.
Usually there is 3 or 4 there and I routinely did a fine tuning with just two engaged.

Either way you are in for a partial disassembly and the best advice is just to get to it and find this screw a home Smile


PostPosted: Wed Apr 10, 2019 4:28 pm    Post subject: Reply with quote

aidaho wrote:
...
Either way you are in for a partial disassembly and the best advice is just to get to it and find this screw a home Smile




Thanks aidaho. You gave me the impetus to go back in. As it turns out it was the three grub screws that sit ahead of the aperture ring. All required a 1/4 to 1/2 turn to tighten up. No more clunking and looseness Smile .

The only thing I can think of is that some of the solution I used to clean the body, got behind the screw heads to the threads and lubricated them.



With regard to the mystery screw. There is a place for a missing screw, but the screw I found is too big for it and has a cross-head rather than slotted -


Here is what it should look like, there are three of them -




The only thing I can think of is that someone lost the original slotted screw and tried to replace it with the cross-head. It didn't fit, 'pinged' away and the owner, not finding the screw, just closed up the lens. As good a guess as any I suppose.


The mystery continues...


PostPosted: Thu Apr 11, 2019 6:41 am    Post subject: Reply with quote

Mmm... car windscreen chip/scratch repair kits. I wonder... [places forefinger on chin and looks to sky for inspiration].



PostPosted: Thu Apr 11, 2019 7:16 am    Post subject: Reply with quote

Sciolist wrote:
Mmm... car windscreen chip/scratch repair kits. I wonder... [places forefinger on chin and looks to sky for inspiration].



Windscreens are parallel glass surfaces so index of refraction of filler material being different from glass doesn’t matter...


PostPosted: Thu Apr 11, 2019 7:40 am    Post subject: Reply with quote

visualopsins wrote:
Windscreens are parallel glass surfaces so index of refraction of filler material being different from glass doesn’t matter...



Good point. I'm going to have to try and work out what effect the filler (or fillers if there are different types) will actually have before going any further. The first thing that entered my head was the possible creation of tiny prisms as you fill a 'v' shaped scratch. I'm out of my depth here and need to read up.


PostPosted: Thu Apr 11, 2019 7:53 am    Post subject: Reply with quote

Sciolist wrote:
Mmm... car windscreen chip/scratch repair kits. I wonder... [places forefinger on chin and looks to sky for inspiration].


I had this thought too.

Wouldn't apply this for scratches, but an effect on chipped element would be interesting to observe.
Large enough chip on the front will show up on photo when lens is heavily stopped down.
While filled up dip in the glass is nowhere near the original in shape and refraction properties, it's still orders of magnitude closer to that than the dip itself, and may help with dark spot.

Anyone have a destroyed lens to volunteer? Smile