Marks on underside of lens glass. Help needed?

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Chris
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#1
Morning guys

I've not posted in the forum in a long time now, but hoping somebody can help me?

Seeing as I'd not used my Sigma 70-300mm in nearly a year, I decided to take it out to sell... Problem being when I checked everything over was that there is a smear/speckles on the underside of the lens glass. Is there anything I can do about this? I'm assuming without removing/cleaning this mark off the lens is useless?

It has been in its case, inside another case in a cupboard in my wardrobe so hasn't been in any unusual weather/surrounding.

Any tips/ advice would be great.

Thanks in advance.

fullsizeoutput_29a2.jpeg
 
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#2
Unfortunately, though hard to be sure looking at it zoomed in on my smartphone, it is fungus. :(

The spots and especially the filaments (what you are describing as smears?) are typical appearance.
 
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Chris Fallon
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#6
Fungus can be cleaned by someone experienced in stripping lenses down, cleaning and rebuilding them. Talk to a Sigma repair agent and explain the problem. For a sigma 70-300, its probably not economically viable to do so.
I'm guessing that's not a cheap option? I only paid £70 for the lens second hand anyway so think i will have to keep it. Maybe I will try a few test shots to see if its noticeable?
 
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#8
I'm guessing that's not a cheap option? I only paid £70 for the lens second hand anyway so think i will have to keep it. Maybe I will try a few test shots to see if its noticeable?
Frankly, I would bin it! I certainly would not be using it and potentially contaminating the interior of the camera and hence 'infecting' other lenses :(

PS as you bought it secondhand, it may have started during the previous ownership and your storing it a long time in an unventilated environment just allowed it to grow?
 
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#9
I can't see to clearly on my tablet but some front glass comes out easily with a lens spanner. If you can see the little notches the tool would fit it might be worth buying a tool and doing it yourself as they're very cheap. If you don't want to bother or it looks too hard I'd keep the lens away from other kit just kn case it could spread.

Or advertise it as possible fungus and spares or repair only and maybe someone will want it.
 
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#10
Wouldn't waste any more time on it, bin is the best place for a fungus infected lens
Just be pleased it was only seventy quid's worth, could have been much worse financially
 
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#11
Exposure to strong sunlight [off camera] or UV light can kill the fungus. Many people continue to use old vintage lenses that were infected, they killed the fungus, it's still there but won't grow or spread - if it doesn't affect images then it's perfectly usable. I would store it well away from other lenses though JIC, with some silica gel packs to prevent any further condensation [what usually causes it to begin with]

Or take it apart and give that element a scrub, soap actually kills it - look up the lens and see if it's an easy one to disassemble. I mean, why not? Again people do this all the time with old lenses, some buy them knowing there's a fungus issue because they know it's an easy enough fix and they get a bargain
 
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#12
As the value is so low, why not attempt to remove the front element and clean it yourself. You will probably find some guidance on the web. Lens spanners are cheap enough on Ebay.

The Lens fungus will grow over time but will unlikely show in images at this stage.
There is no point of being afraid of lens fungus, the spoors are everywhere any way. Lenses kept dry and in airy conditions tend to remain fungus free, those in damp warm closed environments tend to be excellent breading grounds for it. fungus of all sorts like warm and damp and dark.
 
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#13
It could be fungus, but doesn't look right. Fungus generally looks far more hairy than that, spreading from a central point. I have a zeiss planar 85mm f1.4 with a small fungal growth in it. Give it some strong UV exposure and it's dead, not changed in 12 years. That looks more like moisture that has evaporated and left water marks. It could also be the possible beginnings of balsam separation.

Just google lens fungus to see some good examples.
 
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#14
It could be fungus, but doesn't look right. Fungus generally looks far more hairy than that, spreading from a central point. I have a zeiss planar 85mm f1.4 with a small fungal growth in it. Give it some strong UV exposure and it's dead, not changed in 12 years. That looks more like moisture that has evaporated and left water marks. It could also be the possible beginnings of balsam separation.

Just google lens fungus to see some good examples.
If you look at and in enlarge on the Flickr https://flic.kr/p/2hbkgzt View: https://www.flickr.com/photos/127205866@N06/48687325321/in/photostream/
image there is IMO clear filamentous spread.

Though as it was budget price the DIY options mentioned might be worth a punt?
 
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#15
These sort of things get valuable time wasted on them and the vast majority still end up in the bin
Better off enjoying that time for something enjoyable like going out and taking some photos
 
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#16
The price doesn't matter, and even if, £70 might be a lot of money to some. It's a 10minute job with the right tools. There's no harm in trying, you learn something if nothing else that might save a pricey lens some day.
 
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#17
If you're using an APS-C sensor camera then I can't imagine the fungus in that position is ever going to show on an image anyway
 
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#18
If you look at and in enlarge on the Flickr https://flic.kr/p/2hbkgzt View: https://www.flickr.com/photos/127205866@N06/48687325321/in/photostream/
image there is IMO clear filamentous spread.

Though as it was budget price the DIY options mentioned might be worth a punt?
I didn't have that link to the bigger image to go by, but now you've posted it, yep I'll agree that does look like the beginnings of fungus. Certainly doesn't look that bad in the swing of this though. Easily rectified in principal and unlikely to have etched the glass/coatings at this early stage. Really up to the OP if they want to bother or not. If left untreated then there is the risk of it spreading.
 
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Chris Fallon
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#19
Thank you guys really appreciate everyones time.
I'm going to see if I can take it apart myself and clean it up. Being £70 theres nothing to lose right?
Must admit I just thought it was a water/moisture mark until I took the picture and zoomed in on Flickr.
Ah well, like you say - Could have been a whole lot worse and been an expensive lens.
 
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#21
Shame because that aside its in excellent cosmetic condition...

Checked out some online videos and I am not even going to attempt disassembling the lens. Looks far too complicated.
Off to eBay to sell as spares/repairs.

Thanks again guys.
Unlucky, I know that some lenses it's simply a case of removing the disc with the lettering on front and opening a few screws and the front element can be removed, cleaned and put back in place - usually using a piece of tape between element and body, cutting the tape in half to mark where the lens was precisely - then there's lenses that require completely stripping down and I wouldn't go there either.
 
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#23
I would just use the lens without worry - I highly doubt it'll affect your pictures.
Looking at the image I doubt it would affect anything either. I'd hit it with some UV light for a bit and just store it separately to other lenses like I said earlier. I've seen lenses sold with scratches on the front element in worse places and IQ isn't affected [though can be more so with scratches deflecting strong light]
 
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#25
I agree with others that, looking at the picture, there is not enough to worry about here, but if it is not an expensive lens you are worried about, giving disassembling and cleaning it a go can be a fun and useful experience. I found plenty of stuff on the internet about cleaning fungus off lenses. After some research, I used an equal mixture of 25% Ammonium hydroxide and 6% Hydrogen peroxide (food grade). Remove the glass elements, soak them in the solution for about 10-15 mins rubbing the affected areas gently with a cotton bud (obviously, wear rubber gloves and eye protection and do it somewhere well ventilated!). Then wash in several changes of distilled water and air dry. Finally, clean with normal lens cleaning kit before reassembly. I bought the chemicals (in as small a quantity as I could - 250ml and 100ml respectively) off eBay for not very much. Disassembling and reassembling a lens is not difficult (at least for the older, pre-electronic types). Again, there are lots of videos on YouTube. You just need to be really methodical about it and lay out the bits in order as you remove them and make sure to reassemble them in strictly the reverse order. Taking photos of before and after the steps (say, with a mobile) can also helps if you are not sure how stuff goes back together. I cleaned an old Tamron 70-210mm zoom lens which was badly affected and it came out looking like new!
 
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#26
This is what's lived inside my Zeiss 85 f1.4 for over 12 years. It also has a chipped front element, neither issue appears to affect the image quality. It didn't get this during my ownership, but it allowed me to get it extremely cheaply.
KMW_1061
by Kyle, on Flickr
 
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#27
When our house got flooded last year the insurance guy took away my Nikon mk1 70-200 2.8 lens as although it was in the carry case it will get fungus in it( a few members on here agreed)
I was tempted to keep it and to see what happened but glad I took the money although was not as much as I hoped
 
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#28
This is what's lived inside my Zeiss 85 f1.4 for over 12 years. It also has a chipped front element, neither issue appears to affect the image quality. It didn't get this during my ownership, but it allowed me to get it extremely cheaply.
KMW_1061
by Kyle, on Flickr
That's like a work of art all unto itself :LOL:
 
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