Is this $10 Canon FD 50mm f1.4 SSC salvageable?

[toozler]

I bought a $10 Canon FD 50mm f1.4 SSC (the breech-lock version) from someone locally. I saw the lens in person, it had a film of fungus, hence the low price. Otherwise, body was perfect, focus and aperture blades working good.



Disassembled the lens from the front and noticed that all the fungus was on the inner side of the first element. All other elements were clear, just a bit of dust. Took apart the first lens group and cleaned it but the fungus is still there, zero improvement! I tried:

• Water with a drop of dish soap and rubbed with my finger
• Soaked in white vinegar for a few seconds to remove deposits
• Soaked in 3% hydrogen peroxide for 30 minutes
  
• and last a wiped with a lint free lens wipe with 90% alcohol.

Here are some photos. Clear at first sight but shining a light through it shows some "haze". These were taken from the back, thus magnifying everything on the front element. I don't see etching lines (besides some small scratches) but a lot of these tiny dots.



Anything else I should try or is this garbage?
Is this some sort of deposit I couldn't remove or actual damage to the coatings? I've looked around forums and couldn't find a similar pattern.

 

[cramej]

You could polish it with some lens tissue and toothpaste. I did that to a really hazy lens on a Minoltaflex and it went from unusable to pretty nice in a matter of minutes. It was actually a flat lens element so I swirled it around on the countertop with toothpaste. Similarly, this is a lens that really can't be made worse than it already is so there's nothing to lose.

 

[summicron1]

Might not be fungus. Sometimes oil will outgas and etch the glass — this happened to a 2.8 elmar 50mm lens I have - only cure is to replace the element. Given the prices and values of those lenses, Id say you have a really nice $10 lupe.

 

[lensman_nh]

Use it as is and see what happens. You'd be surprised at how much gunk can be on a lens and it still perform OK. Typically issues only really become noticeable in bright sunlight or other high contrast scenarios.

Sometime I think we obsess too much over the state of our optics...

J.

 

[toozler]

Might not be fungus. Sometimes oil will outgas and etch the glass — this happened to a 2.8 elmar 50mm lens I have - only cure is to replace the element. Given the prices and values of those lenses, Id say you have a really nice $10 lupe.

That's a possibility, there was a small amount of oil on the aperture blades. However, this element was not directly exposed to the aperture, there were 2 other lens elements between it and the aperture mechanism and those are in perfect shape.

One the left side of the image you can see that the tiny dots are arranged almost in a straight line running diagonally. Other areas are "clustered" as well

 

[Kino]

Try soaking it in a 50/50 solution of hydrogen peroxide and ammonia overnight.

Clean by running under warm water and then dry with a lens tissue. Next, clean the element it with acetone and a lint free cloth.

If this doesn't clean it off, then you are probably out of luck...

 

[shutterfinger]

Sit it in direct sunlight for 8 to 12 hours or under a high intensity UV light for 4 to 6 hours to kill any fungus in the lens.
Have you tried cleaning the element with your breath and a microfiber lens cleaning cloth?
Even if the dots don't come off it likely won't do more than reduce contrast in some strong side lighting.

 

[toozler]

Thanks everyone for the inputs. It seems there is definitively some permanent damage to the front element, which is a shame, as the remaining elements are flawless.

I'm attaching a few photos. It's perfectly fine under certain light but unacceptable (for me at least) under most light. I'll use as paper weight or sell as-is in case anyone needs parts.

Indoor light behind me - fairly good


Outdoor very diffused light (left image) with a lot of ghosting on high contrast areas. Right image is turining 90 degrees from the sun, very low contrast.

 

[darkosaric]

Outdoor very diffused light (left image) with a lot of ghosting on high contrast areas. Right image is turining 90 degrees from the sun, very low contrast.

Eventually you can try with deep sun shade, it could help.

 

[Kino]

It could be useful in some situations; better than trashing it...

 

[cramej]

Why not give the polishing a try? You can't make it any worse.

Having a lens that you can only use under certain specific light conditions doesn't really do you much good.

 

[bernard_L]

Supposedly one should use Cerium oxide to polish[*] a glass surface. I bought some CeO2 to rescue a Pentacon 135/2.8 with damage on one internal coating. I can send you a small quantity. Just PM me.
[*] polishing is the last step of figuring a lens/mirror, when the shape is correct down to micron scale, but still opalescent.

 

[AgX]

Also, l wouldn't use vinegar on any kind of lens.

Vinegar does not corrode glas*. And with a lens which optical perfomance is hampered by something unwantedly deposited on a lens element surface, the AR coating is the least to worry about.

*There are some special-material lens elements, but the owner of such lens typically knows about such.