[frank]

I just bought a used Nikkor AF-D 28-105mm f3.5-4.5 from a local shop. After carefully checking the lens again after I bought it, I found some brownish material sticked on the rear part of the lens (please see the attached image: inside the two red squares). I thought it could be some "oil leak". I searched the net about oil leak and found that the case of my lens does not look like the often talked "oil leak problem". I touched the outer browndish material with a teeth stick, it is not like liquid.



Can anybody tell me what it is? I hope that it is not some kind of dried oil (otherwise new leaked oil will get into the camera).



Thank you in advance,

Frank

[popo]

Oil doesn't really dry out. Can you get something like a cotton bud on it and see if it's still liquid or not?



Hard to tell from the photo. The other possibility is it could be some kind of thread lock, if there's a screw or similar in the area? It would look shiny and be hard.

[mst]

[quote name='popo' timestamp='1336760845' post='18134']

The other possibility is it could be some kind of thread lock, if there's a screw or similar in the area?

[/quote]



Quite likely. I just checked mine, there are 4 screws below the rear element, which are all covered in thread lock that looks very similar to the marked parts in Frank's image.



-- Markus

[frank]

Thank you both, Popo and Markus. After checking the area more carefully, there is indeed a screw there inside the upper red square area in my image. So, they should be thread lock as pointed out by both of you. While inside the lower red square area, I did not see any screw (but the brownish material looks the same kind). Now I guess it could be some residual of the thread lock material when the lens was assembled.



Popo: I touched the material in the lower red square area with a teeth stick, it is not liquid. It is indeed hard and looks shiny.



Best regards,

Frank