Haze on soft coatings - how do you deal with that?

[p.giannakis]

I have been trying to get a Rokkor MC-II 58f/1.4 in a good condition for some time now. The previous two I bought had to be sent back to the sellers - oil seeps on the aperture blades and people get tempted to clean the whole lens - including oil deposits that evaporated and created haze on inner elements.

Minolta used soft coatings for the inner elements, those "CLA'ed" lenses looked like they were cleaned with sanding paper.

I got a Rokkor MC-II 58f/1.4 that came with an SR-T 101 from the original owner - great condition but slight haze inside (see picture).

This is beyond my repair skills so probably I will send it to Luton Cameras to have it serviced. Any ideas how someone can clean oil from a glass surface without damaging delicate coating?



and the camera/lens combo

 

[Dralowid]

If by 'Luton Cameras' you mean Peter at CCR Luton he has retired.

 

[p.giannakis]

If by 'Luton Cameras' you mean Peter at CCR Luton he has retired.

No, as far as I know it is a different company.

 

[Sonnar Brian]

Probably a combination of the type of lubricant used, and type of glass. Canon lenses of that age are infamous for this. The coatings are not soft. They are not like the old inner Zeiss coatings and Leica coatings. The problem is the type of oil etches into the coating. The Canon 50/1.2 LTM is known for this. Went through 3 to find a good one, and it is very early.
You can send to Skyllaney, they can clean the lens and if necessary- polish it down and recoat it. This is expensive. Maybe worth doing for a Minolta 58/1.2? Not for a 58/1.4. The Minolta Rokkor-X 50/1.4 does not have this problem.

 

[p.giannakis]

Probably a combination of the type of lubricant used, and type of glass. Canon lenses of that age are infamous for this. The coatings are not soft. They are not like the old inner Zeiss coatings and Leica coatings. The problem is the type of oil etches into the coating. The Canon 50/1.2 LTM is known for this. Went through 3 to find a good one, and it is very early.
You can send to Skyllaney, they can clean the lens and if necessary- polish it down and recoat it. This is expensive. Maybe worth doing for a Minolta 58/1.2? Not for a 58/1.4. The Minolta Rokkor-X 50/1.4 does not have this problem.

Thanks for your answer Brian. The previous 58f/1.4 I bought were clear inside but with fine scratches that confirmed in my mind the rumours of soft coatings.

 

[Sonnar Brian]

If the coatings were soft, like on the wartime Zeiss Sonnars: it comes off easily. If the coating is damaged from oil, better to remove it- which I did for one lens.
On this Minolta- someone very aggressively tried to wipe the haze, which was actually damage to the coating. The the coating was soft: it would have come off the glass. That would be better than this.

Nikon has been using hard coatings for inner optics since (at least)1948. I can verify that, after cleaning wax-paper like haze off the inner surfaces on each side of the aperture.

 

[p.giannakis]

Just to conclude with this thread, I decided to open up this lens and try.



luckily the haze was on both elements facing the aperture blades from each side. I very gently cleaned it with diluted Isopropyl Alcohol and cleaned very nicely. As Brian commented above, coatings were more robust than I feared. Of course there was no need to disassemble the grouped elements.

I bathed the aperture mechanism in a cup of Isopropyl Alcohol.



All put togetherand the lens looks and works great. Now it is packed (again) and put under the Christmas tree.

 

[Miles.]

Glad it turned out well!