What does lens "separation" mean?

[artspraken]

gewei shifu,

If seller say lens got "separation", does that mean lens is condemn? can separation be CLA'ed?

thank you in advance

 

[NazgulKing]

In between the lenses, manufacturers would always put some kind index matching fluid in between the lenses. This is to reduce reflections between the surfaces. In this case, because the lenses move as a module, the fluid is a glue. So when the lens separates, it means the glue has degraded and the lenses have moved physically apart.

 

[pegasus21]

I suppose you could send it back to the original manufacturer to get it fixed. Assuming they still service it. In that case, it should be good enough.

If using 3rd party services to cement it back, you could lose the character of the lens... at least that's what I read of people recoating the lens elements of really old lenses.

 

[gommy]

Lenses are make-up glass elements and not all exist as individual element. Some are "grouped" together depending on lens design, that's why we read about lens design being example 7elements in 3 groups etc. Those that are "grouped" are cemented together. Separation usually means the cement between the elements in a group has degraded. If this occurs at periphery usually not an issue but if it's extensive then it will affect the image. The elements can be completely separated and recemented again. I don't think recementing will change the rendition of the lens if done correctly, ie, the elements must be "centred" correctlly.

 

[benny]

Lenses are make-up glass elements and not all exist as individual element. Some are "grouped" together depending on lens design, that's why we read about lens design being example 7elements in 3 groups etc. Those that are "grouped" are cemented together. Separation usually means the cement between the elements in a group has degraded. If this occurs at periphery usually not an issue but if it's extensive then it will affect the image. The elements can be completely separated and recemented again. I don't think recementing will change the rendition of the lens if done correctly, ie, the elements must be "centred" correctlly.

Couldn't have said it better! :thumbsup: Master is master!

Cheers,

 

[pegasus21]

I see. Is there anywhere in SG where we can do these major repair works?

 

[artspraken]

I am now interested to know how to detect separation at the point of sale.

 

[nsng]

Leica developed and used a proprietary glue, ABSORBAN, to cement these elements. I came across this in one of their 70's lens catalog. This glue also acts a a UV filter. Therefore, for Leica lenses there is no necessity to use any filter to reduce UV light other than for protection. If there is separation, it is best to send to back to the factory.

 

[gommy]

I am now interested to know how to detect separation at the point of sale.

Google is your friend....but usually quite easily seen....some examples here:
http://www.google.com/search?q=Lens...7BYb4sAOSlInWCQ&ved=0CEUQsAQ&biw=1547&bih=872

 

[pegasus21]

Hmmm... a thought just occurred to me... assuming you want a 3rd party to repair the separation, wouldn't the repair affect the image if the refractive index of the cement isn't the same as the one originally used?

 

[NazgulKing]

Hmmm... a thought just occurred to me... assuming you want a 3rd party to repair the separation, wouldn't the repair affect the image if the refractive index of the cement isn't the same as the one originally used?

I think it would mean the flare issue will get worse.

 

[pegasus21]

I see. Interesting to know

 

[NazgulKing]

I see. Interesting to know

The use of the index matching fluid is to reduce reflections between the surfaces of the lens. One could of course add a whole lot of other things like Anti-reflection coatings etc. and whatever one wants to add...

 

[bayusuputra]

I think it would mean the flare issue will get worse.

Hmmm... a thought just occurred to me... assuming you want a 3rd party to repair the separation, wouldn't the repair affect the image if the refractive index of the cement isn't the same as the one originally used?

hhmm, i think not only the flare issue will get worse, but i think there may be other things affected.. refractive index affects the way light "bends", so if the refractive index is not the same as the original one, hhmm, i think that will lead to another issue, like softness, or focusing problem, abberation, etc.. but maybe not also, maybe like nazgulking said, it makes the flare issue worse.. so it all depends.. correct me if i'm wrong, though.. haha!

 

[hookonclassic]

Couldn't have said it better! :thumbsup: Master is master!

Cheers,

+1......:thumbsup:

 

[ZoomP]

+1......:thumbsup:

+2!! Words of wisdom from our doctor!

 

[jonmanjiro]

Lenses are make-up glass elements and not all exist as individual element. Some are "grouped" together depending on lens design, that's why we read about lens design being example 7elements in 3 groups etc. Those that are "grouped" are cemented together. Separation usually means the cement between the elements in a group has degraded. If this occurs at periphery usually not an issue but if it's extensive then it will affect the image. The elements can be completely separated and recemented again. I don't think recementing will change the rendition of the lens if done correctly, ie, the elements must be "centred" correctlly.

Kanpeki na (perfect) explanation desu ne!

A while back, a friend had separation between two elements in his Nikkor-N 5cm f/1.1 (a rare, expensive lens so definitely worth getting fixed). He got it repaired by a small but well known Nikon repair shop here in Tokyo (Kiitos), and they did an amazing job. The lens performed like new after the repair job. So there's definitely some smallish repair shops that can repair separation properly. Just need to track down who they are.