How to clean lens element with unknown smudge

[bongsf]

Hi:
This is my first post to the forum. I'd like to ask for your expert knowledge and experience on how to perform lens element cleaning.
For your knowledge I'm not a camera technician and have never received any form of training on lens repair/cleaning. I'm only an amateur shooter for 15+ years so I know how to clean the first and last element, outer surface only
My friend passed me a Ricoh 50 f/1.7 lens, rated at most 3 for the optics. Very dirty, with fungus. Mechanically it's still ok with the focusing ring smooth and aperture ring working. I decided to clean it. Upon closer inspection, I found that I can unscrew the rear optical group with 2 or 3 elements from the lens barrel, so that gave me access to 2 more lens surfaces. I thought since it's a 50, so it's suppose to be simple in design and open up the front ring by unscrewing 3 tiny screws. Then there's the tightening ring on the 1st element. I use a long nose plyer to loosen it and the 1st element came out, followed by the 2nd element. I thought voila, that's not as difficult as I'd imagine . The 3rd element is still in the barrel, but it's reachable from the front and back of the lens. I cleaned all surfaces with Kodak lens cleaner and tissue. I can easily wipe of the fungus and dirt. All internal elements looked clean with no stain remain. However, to my surprise, the exterior surface of the front and last elements are the worst. I can clearly see the front element covered by a layer of smudge ( out of word to describe, not dirt, not fungus, not oil, not moisture) When seeing directly at the surface, there's nothing wrong and the coating looks ok with purple and orange colour. When see through the lens from the rear, that's where the layer of smudge can be seen very clearly. My questions are:

a. Is it due to the cleaning, ie the lens cleaner + fungus + dust mix?

b. Has there been anyone facing the same problem?

c. Or is the element just kaput?

It's really strange as I don't think the 1st element is a cemented 2 element group. But the smudge doesn't look like it's on either side of the element.

Your help is greatly appreciated. Thanks in advance.


regards,
Bong Shau Fui

 

[milosz]

it could be etching of the coating/glass caused by fungi, or else some persistent residue. if first, that is it, what is done is done, there is nothing one can practically and economically do about it. if second, try to gentle clean it with lens tissue moisten with isopropanol- almost no pressure, gentle swipe fast enough to allow the alcohol evaporate as you go. if this does not work, you might try to soak it overnight in isopropanol bath and repeat the first operation....good luck

 

[Christopher Walrath]

Wirelessly posted (BlackBerry9000/4.6.0.167 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102 UP.Link/6.3.0.0.0)

You might try some water and vinegar. The mild acidity of the vinegar might do it and you won't pit the glass.

 

[jfdupuis]

I also have lens like this one. The front element look like dirty and foggy, but all techniques I know for cleaning it didn't work so far. There is only acetone that I haven't tried yet. My best assumption so far is that the glass could have been oxidized with time. My lens seems to be a really old one, so it's believable. After trying acetone, I'll have to conclude that the only cure would be to polish the lens.

 

[Rol_Lei Nut]

I also have lens like this one. The front element look like dirty and foggy, but all techniques I know for cleaning it didn't work so far. There is only acetone that I haven't tried yet. My best assumption so far is that the glass could have been oxidized with time. My lens seems to be a really old one, so it's believable. After trying acetone, I'll have to conclude that the only cure would be to polish the lens.

I know this will sound shocking, but in cases where there is little to lose, I've put glass elements through the dishwasher with success.
Even coated lenses have come out clean and with the coating fully intact.

I've also used the dishwasher to clean very dirty/corroded lens barrels and parts.

Please don't blame me if anything goes wrong, but at least the approx. 10 lenses I cleaned up that way didn't come to any harm (quite the opposite!)

 

[Jim Noel]

LISTERINE - kills the fungus better than alcohol or acetone.
However, it sounds as if this is a 2 lens cemented element and the cement has been attacked by something. If so, I know of nothing that will get in there to clean it.
The strong detergent used in dishwashers will etch glass a little each time it is used.

 

[Rol_Lei Nut]

LISTERINE - kills the fungus better than alcohol or acetone.
However, it sounds as if this is a 2 lens cemented element and the cement has been attacked by something. If so, I know of nothing that will get in there to clean it.
The strong detergent used in dishwashers will etch glass a little each time it is used.

Well, the dishwasher solution that I proposed (in some cases) was intended as a one-off thing... Wouldn't really recommend it on a monthly basis... And of course not for cemented lenses!
;-)

The classic solution of using UV rays to kill funguses is interesting (either using specialized lamps or leaving a lens on an sunny windowsill for a while - I have two on mine now).

Lots of debate on how UV-transparent lenses actually are, and, if exposing them to sunlight will really "disinfect" inner elements.

No harm trying, though...

 

[Terence]

Using a smudge to clean a lens element doesn't sound productive . . . even with a known smudge . . .

Just kidding. Couldn't help myself.

 

[bongsf]

I also have lens like this one. The front element look like dirty and foggy, but all techniques I know for cleaning it didn't work so far. There is only acetone that I haven't tried yet. My best assumption so far is that the glass could have been oxidized with time. My lens seems to be a really old one, so it's believable. After trying acetone, I'll have to conclude that the only cure would be to polish the lens.

I tried VHS tape head cleaning alcohol with no success.

Now I've gathered a few other cleaner/solution: detergent, Listerine, acetone. Just don't understand what happened to that element. I can clearly see the coating is still there, reflecting purple and orange colour. The only explanation would be it is fogged in the cemented surface. But when I took out the 1st element it doesn't look like it's a cemented group. Also, for a normal 50mm design, it's very 'planar' like and don't think it is cemented. I could be wrong though. Now next question would be, what is that 'thing' that form on the element? :confused:

 

[John Koehrer]

As you go along you may have to become increasingly more aggressive. Pretty much as a last resort you can try polishing compounds but need to be aware that you may completely destroy the lens.
I've used toothpaste in the past & it has worked more often than not. It will take damaged coating completely off.