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04-04-2019, 12:39 AM   #1
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Fungus/Degradation on rear element of FA-35-80mm F4.0-5.6

I recently grabbed myself a FA 35-80mm F4.0-5.6 lens from an old MZ-50, and I'm quite fond of it.

While using it in hard sunlight yesterday, I noticed there was a bit of haze, so I shone a torch through it and sure enough there are problems with the rear element.

Thinking (wrongly as it turned out) that the rear element group could be separated into the component lenses and cleaned, I dismantled it on my workbench only to find that it's a single assembly that, as far as I can tell, is firmly bonded together and will not come apart cleanly.

As you can see from the attached photos, the degradation looks pretty bad when you shine a torch through it.

It appears like a number of tangled and branching hairs at various depths within the lens, making me think that the lumen between the elements in the group has been infiltrated. By a fungus - though I do also wonder if it might be some sort of resin failure - I'm unsure of how this particular assembly is bonded together!

I've reassembled the lens (successfully, I might add!) for now - but I would really like to try and sort this if I can, and I'm not sure that sending it off for repair is economical given that I spend 20 on the lens itself.

Any ideas?

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04-04-2019, 02:43 AM   #2
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I think the economical thing is going to be to buy another lens...

The 35-80 is typically one of the least expensive autofocus lenses youll find. So much so that you could probably buy several for what it would cost to fix one...

Id probably go that way.

And if you believe the fungus grew after you got the lens, Id also suggest you check how you are storing your gear. Moisture is not your friend...

-Eric
04-04-2019, 04:37 AM   #3
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QuoteOriginally posted by TwoUptons Quote
I think the economical thing is going to be to buy another lens...

The 35-80 is typically one of the least expensive autofocus lenses youll find. So much so that you could probably buy several for what it would cost to fix one...

Id probably go that way.

And if you believe the fungus grew after you got the lens, Id also suggest you check how you are storing your gear. Moisture is not your friend...

-Eric
My storage is (hopefully) alright - my lenses live in a drawer with a kilo of desiccant at the back that I recharge once a month.

I've actually only had the lens for a few days now - not sure I can be bothered seeking a refund though (even if I'm within my consumer rights to do so - as it is not fit for purpose, and not as described). It seems like a lot of hassle for only 20 (+5 P&P).



I think anything I do will be a DIY-fix - buying a new lens seems to keep them in the same sort of price range (20) - so I might as well try to fix it myself first of all. Worst case scenario, I ruin everything and salvage the lens for my star-guiding project.

Best case scenario, I fix it.



Right... so we have a little assembly containing a group of four lenses.

The lenses are held in a plastic carrier, and may have resin holding the individual elements together - if there is resin it has failed, or is failing, as evidenced by captain fungus and his band of miscreants spreading across the inner surfaces.

So... I need to get inside the lumen of that carrier and abrade the chitinous cell walls of the fungus, without abrading the glass.

I think my first task is to melt a very thin slit with a hot-wire cutter right down the side of the carrier to let me see what I'm dealing with: if the lenses are held in with friction, relieving the pressure of the carrier will allow them to just fall out - if they are cemented into the carrier, then I will put a slit second slit 1/3 of the way round the circumference and try injecting cleaners. By cutting the second slit 1/3 of the way round, any fluids I inject will recirculate on their way round, which will help to remove debris.

I suspect however that the debris will be bonded to the glass itself (probably damaging the coating while it's at it) and flushing won't be enough - in which case I can then pry up that entire segment of plastic while (hopefully) leaving the lenses in position (the second reason why I will make a cut 1/3 of the way round, instead of at the exact opposite side)

With that segment of plastic removed, the lenses might simply fall out - but if not, I can (again, hopefully) get in there with some sort of tool to remove any solid debris - hopefully, once again, not destroying any internal coatings while I'm at it.

If all that fails, I should be able to dislodge the lenses for external cleaning.

I should hopefully be able to get the lens carrier back together using a combination of plastic welds and heat-shrink tubing.



There seems to be a lot of "ifs" in this plan. I certainly wouldn't try it on a brand new lens!

I'll take pictures to show how badly things go xD
04-04-2019, 04:39 AM   #4
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Unfortunately the lens is a loss. The good news is the cost of replacement is extremely low.

04-04-2019, 05:14 AM   #5
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QuoteOriginally posted by Docrwm Quote
Unfortunately the lens is a loss. The good news is the cost of replacement is extremely low.
Well in that case I'm definitely taking it apart and trying to repair it - and when things inevitably go pear-shaped, it's salvage-time!

I'll add another lens onto my wish-list for next month too - might as well be prepared. I wonder if the antique shop has any of these lying around... they definitely have a box of old lenses - but there weren't many pentaxes the last time I checked!
04-04-2019, 05:21 AM   #6
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QuoteOriginally posted by cprobertson1 Quote
Well in that case I'm definitely taking it apart and trying to repair it - and when things inevitably go pear-shaped, it's salvage-time!

I'll add another lens onto my wish-list for next month too - might as well be prepared. I wonder if the antique shop has any of these lying around... they definitely have a box of old lenses - but there weren't many pentaxes the last time I checked!
The old FA28-80, 35-80, & 28-105 lenses are very inexpensive around here. The best rated are the FA28-105 Powerzoom and 28-70 models.
04-04-2019, 05:40 AM - 1 Like   #7
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QuoteOriginally posted by Docrwm Quote
The old FA28-80, 35-80, & 28-105 lenses are very inexpensive around here. The best rated are the FA28-105 Powerzoom and 28-70 models.
20-30 (delivered) seems to be the going rate for the 35-80mm. I mainly want it as a walkabout lens that fits nicely between my 18-55 and 50-200mm lenses - so it's definitely not a big deal.

Side note, I love that silver colour


I'll need to check the 28-80 and the 28-105 lenses too - I'll add them to the ebay watchlist. Speaking of which, I had better start asking sellers to shine torches through their lenses before I buy them - though I suppose I've been lucky up until now (apart from that one lens that I sent back because it had springtails living in it (meaning it was definitely humid, and had likely had fungus living on or near it for the springtails to eat)...

--EDIT--
The 35-80mm lenses seem to be the 20-30 range on ebay just now, while the 28-80mm are 30-60, and the 28-105mm seem to be going for 100+

--EDIT-WITHIN-AN-EDIT--
Boom, another FA 35-80mm for 12 delivered. The one I currently have is now officially "expendable"

::Whispering:: I just had a really fun idea that is actually-not-entirely-crazy... springtails are small (0.3-0.5mm) and eat fungus... sure, they leave frass, but it's water soluble... I wonder if I could introduce them to the rear lens group (again, cutting a slit down the side as above) and let them live there for a little while, and then asphyxiate them with CO2 and wash them out with water before finally drying with nitrogen and sealing it all up.

What could possibly go wrong!?

Last edited by cprobertson1; 04-04-2019 at 05:46 AM.
04-04-2019, 06:29 AM   #8
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That 35-80 is a really nice lens. If you don't pixel peep, it was actually preferred by 28% of forum respondents in this poll of the lenses I tested. Pixel peeping only 7%. A great, lens for taking pictures to post on the forum. The one above probably had water inside and was never dried properly. Mine has bit of dust but is still an excellent lens.
35mm find that prime. - Page 2 - PentaxForums.com

04-04-2019, 07:35 AM   #9
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QuoteOriginally posted by normhead Quote
That 35-80 is a really nice lens. If you don't pixel peep, it was actually preferred by 28% of forum respondents in this poll of the lenses I tested. Pixel peeping only 7%. A great, lens for taking pictures to post on the forum. The one above probably had water inside and was never dried properly. Mine has bit of dust but is still an excellent lens.
35mm find that prime. - Page 2 - PentaxForums.com
I really liked it, even in spite of it's fungal infection. Hopefully my second one will be less moldy!

Somewhat paradoxically, a good few of the pics I took with that fungally1 lens had reasonable sharpness and the contrast wasn't terrible... provided the image was underexposed slightly. When I went out in the sun with the (white) doggie, it was like he had an holy aura around him

Maybe he's a ghost dog. Now tell me you wouldn't watch a show about a ghost dog that is only visible in film and gets befriended by a mentally disturbed photographer who despite many years with his ghostly canine pal still can't decide whether or not it's all in his head?2

1Why yes! "Fungally" is a real word! When I typed it in, it felt weird, so I double checked
2Arent brain-tangents fun?
04-05-2019, 12:19 AM   #10
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Okay - so I took apart the rear element group last night - ended up having to slice it open with the hot wire.

It turns out I could have done this with only one slit - in fact, I might even have managed to get away with just a hole to poke one of the lenses out the end and then pushing the rest out with my finger.

Oh well!

Anyway, I took it apart and treated it with hydrogen peroxide/acetic acid solution and gave it a wipe with a microfibre cloth, and managed to weld it back together with no problems
So, wow - I may not always have good luck, but when I'm good, I'm good. (if I do say so myself ) - I was expecting it to fail miserably!

Unfortunately, as I wasn't expecting to have much success, I didn't do this in a cleanroom environment, and I introduced a ton of dust... BUT I cleaned off the fungus, and once I get the lab cleaned out I'll get the air pump and clean-box running and go in and clean it out properly and hopefully restore it to close to its original IQ (fingers crossed!)

As you can see from the images, it's still pretty dusty - but it's definitely better than what it was (not perfect, but at least the haze is gone!) I'll get before/after pics up shortly.








---------- Post added 04-05-19 at 12:37 AM ----------

Note that there's a lot of internal/stray refraction in the last image - I took the photo at an angle to backlight the contaminants without shining the torch directly into the camera - I swear it doesn't look that bad in real life!

Ps - the lens coating has probably suffered a little, though I did take care to minimise abrasion to it, Captain Fungus and his band of Mycelial Miscreants weren't so careful.

Last edited by cprobertson1; 04-05-2019 at 12:34 AM. Reason: Converting attachments to album images for better layout
04-05-2019, 11:20 AM   #11
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Congratulations and nicely done! Gives me hope to tackle a zoom of my own with a hazy rear group.
04-05-2019, 11:58 AM   #12
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My thoughts on all your efforts, is I would probably keep that lens segregated from your other lenses. Mold/Fungii spores can be small and move around. The problem with these lenses is often their ability to be contagious to other lenses. That's not to say it will happen, but it is a risk, especially since you opened the lens up.
04-06-2019, 04:17 AM   #13
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QuoteOriginally posted by emalvick Quote
My thoughts on all your efforts, is I would probably keep that lens segregated from your other lenses. Mold/Fungii spores can be small and move around. The problem with these lenses is often their ability to be contagious to other lenses. That's not to say it will happen, but it is a risk, especially since you opened the lens up.
That might be a plan!



I'm actually of two thoughts on this - see, we have two scenarios regarding the type of fungus that is in the lens, and one greatly increases risk of cross-contamination, and the other only marginally increases risk.
1) This fungus is specific to camera lenses.
2) This fungus is a generic fungus that got lucky and landed on a lens that had the right conditions for growth.

In both cases, fungal growth requires specific conditions: it needs an energy source (food, sunlight), water, and a gas supply (oxygen or CO2 depending on how it's getting the energy).

With these constraints, you can see that lenses aren't a good place for fungi - gas flow is low, so the rate of growth, even under otherwise optimum conditions, will be severely limited - and even if it's getting plenty of oxygen, water is limited and growth will slow to a crawl once it's used up

The thing to remember is the air is always full of spores (and bacteria) (and occasionally small mites) (don't forget the viruses!) (and the viruses that infect the bacteria and the fungi) (and the fungi that infect the bacteria and the mites) (and the bacteria that infect the fungi and the mites)

Air is gross. In fact, EVERYTHING is gross. "Everything" is one of the more important reasons for having an immune system xD.



ANYWAY - so you always have a population of fungal spores - present, and this brings us back round to our two scenarios - that of a lens-specific fungus, and that of a generic fungus seeking any dark area of trapped moisture.

As far as I am aware, the scenario of a lens-specific fungus is unlikely for the simple reason that there isn't enough selection pressure - if there was something particular about lenses that allowed them to present a unique environment for a particular fungus, then sure - but usually fungi would actually proliferate better in the environment where your lens is stored than in the lens itself!

A lens-specific fungus would greatly increase the risk (from close-to-zero, to whatever the transmission risk is) - while a generic/opportunistic fungus being present in one lens doesn't really increase risk in the other for the simple reason that the fungal spores are already in the the air regardless of the presence of the infected lens.

With all that in mind, you can see that it is unlikely for fungus to spread from one lens to another unless both lenses are already in an environment that promotes fungal growth - in which case, opportunistic fungi will also infect your lens. Where the problem might arise is that your infected lens may "seed" the other lens - but again, this is all dependent on the environment providing sufficient moisture (and something for the fungus to consume for energy). So - it may increase risk of cross contamination, but only marginally, and in environments that already promote fungal growth.

This would explain why there appears to be a lot of conflicting data on fungal spread - the presence of fungus in one lens acts as a seed for the other lens - but spores would have been present anyway: so rather than being the cause of the infection in a clean lens, it instead speeds up the rate of initial infection - but the actual cause of the infection is the moisture, which allows any fungus to grow.

Yum!

The moral of the story seems to be "don't moisten your lenses"




That said, even if the increased risk from having that lens near my other lenses is minimal, I think I'll move the post-infected lens onto astro-tracker duty, which will keep it away from my good (plus it's lighter than my minolta lens that I had earmarked for the same purpose). I also think it's a better lens than the minolta xD

---------- Post added 04-06-19 at 04:18 AM ----------

Ooops, meant to say, I'm going to make a video on dismantling that lens when I go back and dust the rear elements for a clearer view
04-06-2019, 08:47 AM   #14
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QuoteOriginally posted by cprobertson1 Quote
The moral of the story seems to be "don't moisten your lenses"
My solution exactly. I moved from Hawai'i to Colorado and solved all my fungus problems.

Thanks for a fun to read thread!
04-08-2019, 08:57 AM   #15
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QuoteOriginally posted by cprobertson1 Quote
That might be a plan!



I'm actually of two thoughts on this - see, we have two scenarios regarding the type of fungus that is in the lens, and one greatly increases risk of cross-contamination, and the other only marginally increases risk.
1) This fungus is specific to camera lenses.
2) This fungus is a generic fungus that got lucky and landed on a lens that had the right conditions for growth.

In both cases, fungal growth requires specific conditions: it needs an energy source (food, sunlight), water, and a gas supply (oxygen or CO2 depending on how it's getting the energy).

With these constraints, you can see that lenses aren't a good place for fungi - gas flow is low, so the rate of growth, even under otherwise optimum conditions, will be severely limited - and even if it's getting plenty of oxygen, water is limited and growth will slow to a crawl once it's used up

The thing to remember is the air is always full of spores (and bacteria) (and occasionally small mites) (don't forget the viruses!) (and the viruses that infect the bacteria and the fungi) (and the fungi that infect the bacteria and the mites) (and the bacteria that infect the fungi and the mites)

Air is gross. In fact, EVERYTHING is gross. "Everything" is one of the more important reasons for having an immune system xD.



ANYWAY - so you always have a population of fungal spores - present, and this brings us back round to our two scenarios - that of a lens-specific fungus, and that of a generic fungus seeking any dark area of trapped moisture.

As far as I am aware, the scenario of a lens-specific fungus is unlikely for the simple reason that there isn't enough selection pressure - if there was something particular about lenses that allowed them to present a unique environment for a particular fungus, then sure - but usually fungi would actually proliferate better in the environment where your lens is stored than in the lens itself!

A lens-specific fungus would greatly increase the risk (from close-to-zero, to whatever the transmission risk is) - while a generic/opportunistic fungus being present in one lens doesn't really increase risk in the other for the simple reason that the fungal spores are already in the the air regardless of the presence of the infected lens.

With all that in mind, you can see that it is unlikely for fungus to spread from one lens to another unless both lenses are already in an environment that promotes fungal growth - in which case, opportunistic fungi will also infect your lens. Where the problem might arise is that your infected lens may "seed" the other lens - but again, this is all dependent on the environment providing sufficient moisture (and something for the fungus to consume for energy). So - it may increase risk of cross contamination, but only marginally, and in environments that already promote fungal growth.

This would explain why there appears to be a lot of conflicting data on fungal spread - the presence of fungus in one lens acts as a seed for the other lens - but spores would have been present anyway: so rather than being the cause of the infection in a clean lens, it instead speeds up the rate of initial infection - but the actual cause of the infection is the moisture, which allows any fungus to grow.

Yum!

The moral of the story seems to be "don't moisten your lenses"




That said, even if the increased risk from having that lens near my other lenses is minimal, I think I'll move the post-infected lens onto astro-tracker duty, which will keep it away from my good (plus it's lighter than my minolta lens that I had earmarked for the same purpose). I also think it's a better lens than the minolta xD

---------- Post added 04-06-19 at 04:18 AM ----------

Ooops, meant to say, I'm going to make a video on dismantling that lens when I go back and dust the rear elements for a clearer view
Obviously you've thought about it, but I'll just give you one other thought (I work in risk, albeit for floods and earthquakes and preventing loss, so the risk is a bit different here).

Let's say the risk for fungus in a lens is 0.1% (1/1000); I'm not sure what it really is, but that is probably reasonable and perhaps 1/100 if you live in a more humid environment (and a lot lower if you live in a desert).

So having that lens with mold on it could increase your mold by some factor, and in risk those factors are usually on orders of magnitude. So while perceptually low, the presence of that lens increases the risk by a factor of 10 (e.g. 1%). This isn't saying anything about where the fungus comes from but just the presence. Basing it on some percentage (.1% or 1% accounts for the limited likelihood based on environmental factors like you listed vs. 100% (guaranteed to get it) or 50% (essentially a count flip).

Ok. So let's say the presence of a lens with a fungus in it (regardless of where the fungus comes from) increases the risk to a 1% chance you'll get the fungus in another lens. Well, this would mean that if had 100 lenses you would be all but guaranteed to to get the fungus in one other lens. If you only have 10 lenses, then there is a 10% chance one of them would get it.

All I am getting at is that while risks can be small when considered on an individual basis, they can be significantly higher when you have a large population. A situation occurred where a lens got a fungus, and that automatically increases risk. And while the risk of another individual lens getting the fungus may still be low (but now a bit higher), the odds of another lens getting it increases as you have more lenses. The caveat on risk in general is just how much you are willing to accept the risks. With lenses, this isn't a life, so it really isn't that big of a deal, it is just statistics. The starting risk may be much lower (or higher than I gave) but the relative change in risk is probably correct. Once a lens has gotten a fungus, there is probably a 10 times increase in risk that another will get one, and then it goes up more by a factor based on how many lenses you have.

On a side note, this is a difficult we face in my job. When we design structures for a 1/2500 risk, we still get failures because there are often way more than 2500 structures that face an earthquake. Once we have over 2500 structures, we are all but guaranteed one will fail. Travel is similar (planes vs. cars); The odds of plane crashes are much lower than those of cars, but when you tally up the number of cars vs planes (and the number of flights), both end up happening because there is no such thing as zero risk; there are 32million plane flights per year in the U.S. If even if the risk of a plane crash is 1 in 10million, that says there will be 3 plane crashes per year in the U.S. alone.

Thankfully lenses aren't lives lost, but it's also a lot easier with lenses to lower the risks (or be willing to deal with the consequences if the risks become reality).

Sorry for beating a dead topic but rather just pointing out how even low probability events can become more probable and risky.
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