Luminous Landscape Forum

Equipment & Techniques => Cameras, Lenses and Shooting gear => Topic started by: Ed Blagden on December 06, 2018, 07:28:29 am

Title: Lens Fungus - woe is me!
Post by: Ed Blagden on December 06, 2018, 07:28:29 am
Looking for some advice here.  I have an old Sigma EF mount 70-200mm f/2.8 EX lens, which I bought way back in 2001.  I haven't used it for years but the other day I took it out for some landscape shooting and when I got the images into Lightroom I could see that something was definitely off, so I took a close look at the lens and saw what looks like a patch of fungus on one of the rear elements.  Bother, blast etc.  I attach a photo of the offending lens.  It looks much worse in the photo than it does in normal light - I took this on a light table and angled the camera just-so to catch the light.

I emailed a few UK camera repair outfits plus Sigma UK as well, to ask if cleaning / repair was possible.  Sigma wrote back to say sorry, no, the lens is so old we won't have parts for it.  Two others wrote back saying yes, send it in and we will clean it up for you no problem.  One of those quoted 120, the other just said they would give me an estimate once they had the lens.  Finally, another repairer wrote back saying that while they could clean it they didn't recommend it, because once a lens has fungus it always comes back very quickly and they didn't want to take my money for what would be in effect a useless repair.

I'm curious if anyone here has experience of having a fungus infested lens cleaned up - did it work and did the infestation come back anytime soon?  If a repairer is telling me not to bother then on the face of it I should take that seriously, but maybe they are being over cautious. 

What do folks here think?
Title: Re: Lens Fungus - woe is me!
Post by: NancyP on December 06, 2018, 11:41:00 am
Where is the fungus? Sitting on the exposed surface of the rear-most element? Or is it inside?

Article on DIY fungus removal, requires willingness to open up the lens, and some tools which you may not have (Japanese-standard screwdrivers, lens wrench, etc). :

There is at least one repair video, unclear if it is your model. Youtube blocked at my site now. Google "sigma 70 200 f2.8 old schematics" or "sigma 70 200 f2.8 old repair". Service manuals are hard to find, I suspect that the companies regard the manuals as secret intellectual property and threaten to sue people who post service manuals unless the service manual is taken offline immediately. A few manuals are out there for 50 year old lenses - I scanned for old AIS or pre-AI Nikkor lenses - a few service manuals are out for some pre-AI lenses ( ~ 60 years old). Not mine - I want to refresh helicoid grease on an ancient 50 mm f/1.2.

Best is to prevent fungus by storing lens in dehumidified environment. People who live in subtropical climates use special storage chambers:
First brand listed by B and H (there are several more):

Title: Re: Lens Fungus - woe is me!
Post by: Ed Blagden on December 07, 2018, 07:42:57 am
Thanks - but I can promise you I really have no intention of working on this lens myself when there are plenty of independent repair shops who will do the work for me!  I know my limitations.  My real question is whether there is any point in cleaning up fungus: will it come back quickly as one of the repair shops asserts?

To answer your question the fungus is inside the lens, on one of the rear elements.
Title: Re: Lens Fungus - woe is me!
Post by: degrub on December 07, 2018, 08:57:45 am
the real issue is if the fungus has attacked the coating on the lens element if there is one.
If the fungus has "fruited" and created spores, it may not go away, and will just wait for a period when the humidity is right to sprout and grow.
So you can try the cleaning, but if there are damaged coatings, it may not change the result much.
If you do clean it, you will have to store the lens in a low humidity box to slow down the regrowth as Nancy mentioned.
All in, it might be cheaper to find another lens.
good luck.
Title: Re: Lens Fungus - woe is me!
Post by: Rajan Parrikar on December 07, 2018, 01:02:38 pm
My Zeiss 100 Makro Planar lens had an infection in 2013. Zeiss refused to deal with it. I finally found John van Stelten in Colorado who handled the cleaning with great skill.

I see that he has now closed shop.

Title: Re: Lens Fungus - woe is me!
Post by: Rhossydd on December 07, 2018, 02:30:25 pm
the real issue is if the fungus has attacked the coating on the lens element if there is one.
The difficulty is that the amount of damage won't be known until it's cleaned off.

With fungus on it the secondhand value is likely to be very low indeed. I'd be tempted to have a go at taking it carefully apart to see how bad it was and if it cleaned off OK, passing the parts to a repairer to reassemble(if it was tricky).
If it really is just the back element it might not be too risky, but it might be much deeper into the lens assembly than it appears.
Title: Re: Lens Fungus - woe is me!
Post by: NancyP on December 10, 2018, 02:12:12 pm
I daresay that most repair shops aren't happy to have fungus lenses on their premises.

I would suggest just "airing out" your other unused lenses once a year - set them, cap off, no UV filter, in the sun (not behind window glass, ideally) for a day or two - or if you have a grow-light, set them under the grow light. You want UV exposure to damage the DNA of any possible lurking organisms.

If you can afford it, buy another lens. May I suggest the Canon 70-200 f/4L IS v. 1? There should be some used ones out there now that Canon has issued a version 2. USD $400.00 to $700.00. (OK, I am the ugly American  :-[ , not conversant with current UK pound-USD rate) The version 1 is a fine lens for landscape, and a lot lighter than the f/2.8 lenses.
Title: Re: Lens Fungus - woe is me!
Post by: phila on December 14, 2018, 09:47:24 pm
As an ex-camera technician I can say that if the lens surface affected is coated then you will be left with a 'fungus shaped' mark on the surface after it has been cleaned. This may/may not have a noticeable effect on your images. Replacing the affected individual lens/group is the only surefire repair. However you would need to make sure that there isn't any fungus remaining in the lens. If the parts are no longer available then (assuming you are particularly attached to the lens it make the effort worthwhile) buying another one and cannibalising it for parts might be an option.
Title: Re: Lens Fungus - woe is me!
Post by: BrianVS on December 27, 2018, 03:52:10 pm
The damage is often caused after the fungus has died and etched the coating or glass. If you get to it quickly- there is a chance it can be cleaned off completely. I've done this on RF lenses, coated and uncoated. Fungus is spread by Spores- the cleaning the lens and storing it in a dry area is important. Keeping it out of the case it was in is a good idea.