How are we on lens disease?

Peter B

Peter B

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This is an old (30+?) Tamron SP90 macro lens which I have only used a couple of times in the past 20 years or so, but it has developed a strange affliction as shown in the photos. It looks to be inside the front element, and it isn't what I understand as fungus. I don't think the lens is worth repairing, although I might just satisfy my curiosity and try taking it apart myself.

20180318_114812_resized-tp.jpg 20180318_114910_resized-tp.jpg
 
Wow never seen anything like that...maybe element separation, but you would have to see exploded view of the elements to see if the front ones are glued together. From the few lenses I've taken apart the front one is usually a single so maybe it is not that.
Anyway you can't lose by unscrewing the front dust cover and cleaning with lighter fuel or whatever.
 
It looks like lubricant. If the lens got hot, lubricant can become runny and flow onto the glass. It certainly is not fungus. Does it affect the image at all?
 
john.margetts said:
It looks like lubricant. If the lens got hot, lubricant can become runny and flow onto the glass. It certainly is not fungus. Does it affect the image at all?
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I'm not sure as I haven't run a film through with it and my digicams aren't full frame, so won't use the edges of the lens. I'll certainly be trying it next time I put a film in the camera.
 
Peter B said:
and my digicams aren't full frame, so won't use the edges of the lens.
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They will, you know. All parts of the image are formed by all parts of the lens.. The edges of the image circle are formed as much by the centre of the lens as they are by the edges of the lens. Aperture is another thing entirely, a smaller aperture does not use the edges of the lens but that a does not reduce the size of the image circle.
 
john.margetts said:
They will, you know. All parts of the image are formed by all parts of the lens.. The edges of the image circle are formed as much by the centre of the lens as they are by the edges of the lens. Aperture is another thing entirely, a smaller aperture does not use the edges of the lens but that a does not reduce the size of the image circle.
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So if the mark is at the top of the lens when it is fitted to the camera, remind me whether it is affecting the top or bottom of the picture?
 
Doesn't look like fungus to me either - I think the suggestions of elements/coating are probably on the money.
 
I had one almost the same, turned out to be oil from the iris blades.
It did come off though, but the lens had to be dismantled and serviced by a professional.
He said it can happen if left in the sun (heat) for a while. (I left it in my car on the front seat for about 3 hours)
 
excalibur2 said:
It looks like the front element is a single http://adaptall-2.com/lenses/52B.html so should be easy? to take out and clean the back.
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Thanksfor the link Brian. It had been sitting in the back room for a couple of weeks, but the central heating has never been above 21.5C. I wouldn't have thought it would get damaged, but maybe that was enough for it to suffer this.
 
On some lenses when you unscrew the dust cover (with something like a rubber drain plug) the front element drops out, but others might fastened in place some way. Good luck.
 
Peter B said:
So if the mark is at the top of the lens when it is fitted to the camera, remind me whether it is affecting the top or bottom of the picture?
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It is affecting ALL the image. If the mark is on the rear element it might cause a localised blurring at small apertures. Towards the front of the lens, it effect will be either lose of contrast or flare - but all over the image.
 
Just watched a video where the camera repair guy describes using 2 flat screwdrivers to remove the front ring as "a crime". He also says that using tweezers to try the same is also a crime. Guess I'll be sending for one of those spanner/wrench type things then.:thinking:

Not the world's greatest photo, but Im not seeing any real problem in this quick shot.



DSCF1349-tp.jpg
 
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I'd use two tiny flat blade screwdrivers with a bar in between, if it was a thousand pound lens then I'd think different. Just be careful I've done it that way dozens of times in my youth working as a Photographic engineer in industry.

Take your time and save some money, just be careful tp note which way the lens comes out, putting a little bit of tape on the front helps.
 
ChrisH said:
I'd use two tiny flat blade screwdrivers with a bar in between, if it was a thousand pound lens then I'd think different. Just be careful I've done it that way dozens of times in my youth working as a Photographic engineer in industry.

Take your time and save some money, just be careful tp note which way the lens comes out, putting a little bit of tape on the front helps.
Click to expand...
Ah well, I've already taken a touch of paint off the ring when the flat screwdriver slipped, so I'll probably just go for the spanner. :oops: :$
 
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