How does fog in lens happen?


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TrailsofLife

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Jul 6, 2004
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#1
Recently I saw some misty thing inside one of my lens, so I sent it in for cleaning. Turn out, the technician told me its fogged and he will need to replace 2 of the elements.

Forgot to ask him, so post the question here, What actually happen when a lens fogged up?
 

Goldenstars08

Senior Member
Nov 21, 2004
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#2
Max 2.8 said:
Forgot to ask him, so post the question here, What actually happen when a lens fogged up?
It is like you add a soft filter in fount of the lens...:bsmilie:
All the image taken is blur...:confused:
 

Dennis

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Jan 24, 2002
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#5
Don't understand what the technician is trying to say, fogging normally means mist on the lens i.e. taking from cold to warm area. Unless he is trying to say that there are fungus in the lens that cannot be removed so he had to replace the elements. Seldom heard of fogging in this context. :dunno:

Max 2.8 said:
Recently I saw some misty thing inside one of my lens, so I sent it in for cleaning. Turn out, the technician told me its fogged and he will need to replace 2 of the elements.

Forgot to ask him, so post the question here, What actually happen when a lens fogged up?
 

Goldenstars08

Senior Member
Nov 21, 2004
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#6
Dennis said:
Don't understand what the technician is trying to say, fogging normally means mist on the lens i.e. taking from cold to warm area. Unless he is trying to say that there are fungus in the lens that cannot be removed so he had to replace the elements. Seldom heard of fogging in this context. :dunno:
Think that you are very lucky...Never encounter fogging before...:angel:
For a fogged lens, one or more elements will look misty for ever. Even you let the lens in room tamperature forever, is still like that...Now you should understand lor...:kok:

Need to learn by experience...:bsmilie:
 

Dennis

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Jan 24, 2002
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#7
Mmmm have seen lens like that before but I thought it was another type of fungus.
Not sure what caused it but you are right I have never had a lens like that before maybe it is because I always take care of them.

Goldenstars08 said:
Think that you are very lucky...Never encounter fogging before...:angel:
For a fogged lens, one or more elements will look misty for ever. Even you let the lens in room tamperature forever, is still like that...Now you should understand lor...:kok:

Need to learn by experience...:bsmilie:
 

timlim

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Mar 10, 2005
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#8
what lens is it? how much did it cost to replace the elements?
 

MDZ2

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Feb 23, 2005
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#9
It is a degradation of the lens coating. I was told Sigma lenses have a tendency to suffer from such effects. I have a 16mm lens that has the same problem.
BTW, how much did you have to pay for the replacements?
 

fuwen

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Aug 11, 2004
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#10
It's lucky that the lens elements can be replaced. I have seen fogging in old lenses before. It could be design and material used issue rather than whether the user takes care of the lens or not. I think the most likely reason is the cement that glue 2 elements together to form one optical group deteriorated over times. There are probably other reasons but the bad thing is this fog cannot be clean but can only be replaced.
 

sulhan

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May 11, 2002
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#11
Hiee...

Had a couple of experience for fogged len.

The fogged lens surface apparently will look like little fine dots quite equally spaced on the lens element. Apparently, the fogging on some lens is caused by grease vapor deposited on the lens when the lens, after several "sun-tanning" session out in the sun (especially black lens) when it get really hot in the lens barrel. Greasing used on some parts may vapourise and when th elns goes indoor, the inner glass which is normally glass cools faster and hence the vapour which have no where to escape may deposit on the lens element. Usually, the repair would be a one to one change if the lens element is in a flxed module where they cant open due to glued group or in some cases the grease had actually damage the anti reflection coating on these lens.

Fogged lens notmally gives glowing feel to the output at wide open as the dots diffuse light rays. Stopping down may help a little.

SO just be extracareful if getting used lens. Try to look and focus with you reyes through individual layers of lens element in the glass if possible. Dont just look from far. If can bring a little flash-light and shine from the front and if its fogging in the rear element, you can usually see it clearly.

rgds,
sulhan
 

Jemapela

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Feb 20, 2005
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#12
Max 2.8 said:
Recently I saw some misty thing inside one of my lens, so I sent it in for cleaning. Turn out, the technician told me its fogged and he will need to replace 2 of the elements.

Forgot to ask him, so post the question here, What actually happen when a lens fogged up?
A lens technician (from Yashica) told me that fogging is caused by heat.

Other sources (in other forums) also say that it's caused by heat, and they go further to say that it's due to inferior quality elements (very possibly some kind of plastics used to make the elements, and not glass). Some third party lens makers use plastics to make their elements. They boast of lightness, but not so much of durability or quality. If you think about it, it quite makes sense because plastics degrade over time, especially with heat.

Others, but fewer, say it's inferior quality coating but I doubt this theory. They are also few others who say that it's the lubrication inside the lens barrel which evaporates in the heat, forming a vapour which stains or affects the coating.

MDZ2 is quite correct to say that Sigma tends to have this problem. In other forums, other Sigma owners have also mentioned it.

I have a Yashica lens which fogged up badly but it's cheap and I'm not hurt.

Also, I have a Sigma 400mm APO lens which has fogged up badly. It appears that 1 element inside fogged. The rubbery exterior has also become sticky due to S'pore's heat. It's a useless paperweight in my dry cabinet. It was NEVER used at all because I didn't take it with me to Australia where I now live and work. Needless to say, you can understand how sore I'm with Sigma.

Just out of curiousity, which lens of yours fogged? How much is it costing you to repair?
 

TrailsofLife

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Jul 6, 2004
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#13
Thanks for all the answers... Just proved that the Canon's "so called" premium L lens also have crap elements inside...

Mine was a 70-200 f2.8L, paid 490+ for the elements changed...In the end got a new one in replacement because Canon's courier dropped my lens!
 

Jemapela

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#14
Wow! Was it the older (non IS) version?

I have one such lens too but it doesn't seem to have fogging even though it's kept in the same environmental conditions as the others which fogged.
 

TrailsofLife

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#15
Yes, its the non-IS version. Just stop using for about 3 months, fogged already.
 

solarii

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Oct 20, 2005
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#16
Max 2.8 said:
Thanks for all the answers... Just proved that the Canon's "so called" premium L lens also have crap elements inside...

Mine was a 70-200 f2.8L, paid 490+ for the elements changed...In the end got a new one in replacement because Canon's courier dropped my lens!

That goes to show you the state of modern day manufacturing practices. Even premium products cut corners to save on costs. They don't build things to last as they used to.
:cry:
 

TrailsofLife

Senior Member
Jul 6, 2004
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#17
solarii said:
That goes to show you the state of modern day manufacturing practices. Even premium products cut corners to save on costs. They don't build things to last as they used to.
:cry:

So does their service...:cry:
 

MDZ2

New Member
Feb 23, 2005
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#18
Max 2.8 said:
Thanks for all the answers... Just proved that the Canon's "so called" premium L lens also have crap elements inside...

Mine was a 70-200 f2.8L, paid 490+ for the elements changed...In the end got a new one in replacement because Canon's courier dropped my lens!
$500!!!!:bigeyes: Looks like I too will be using my lens as a sticky paper-weight :cry:
Lucky I didn't pay much for it and managed quite a few sessions with it. :D
 

donchua

Senior Member
Nov 30, 2004
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Tampines
#19
Max 2.8 said:
Thanks for all the answers... Just proved that the Canon's "so called" premium L lens also have crap elements inside...

Mine was a 70-200 f2.8L, paid 490+ for the elements changed...In the end got a new one in replacement because Canon's courier dropped my lens!
Finally you got a new replacement because of the drop.

BTW, fog are in dots or misty patches?
 

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