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[Aphototaker]

Hello.
 
On a recently acquired FD 50mm f/1.4 lens, I have noticed that the diaphragm gets some kind of a fluid on it as it is worked. If I leave the lens aside for a while, that wetness disappears as if it has evaporated.
 
Also, on of th

[David_nebenzahl]

Dunno what the fluid is, but it doesn't matter: you don't want it there. Diaphragm blades should be bone-dry. That haze is probably whatever the fluid is, deposited on the inside of the lens. Should be easily removable with the usual lens cleaners

[Aphototaker]

I suspect, though I may be wrong, that the fluid is coming from the inside mechanism of the lens and is not just on the blades.
 
In any case, does the behavior sound like it is oil? The fact that it is disappearing makes me think it is not oil

[David_nebenzahl]

Well, we can pretty much rule out it being water, which leaves any number of oil-based substances. It may not be oil per se, but is probably some kind of petroleum product. Could be some component of the grease used on the focusing helical, I supp

[Aphototaker]

I have noticed that the focusing ring is a bit hard to move. It does rotate, and is smooth, but takes some effort. Could this be related somehow? And the aperture ring is a bit too easy to move (the dedents are soft).
 
It is a Canon FD 50mm f/1.

[Gez]

It's oil. The FD 50mm/1.4 made about 1977 are notorious for this problem. The oil doesn't evaporate, it merely spreads out onto the blades with increase in ambient temperature. There is lots in the archive on how to clean the 50/1.4 iris assembly,

[Tom_cheshire]

It sounds very much like your newly acquired lens was repaired recently by a (choose the insulting word yourself) repairman.  
 
The aperture probably has lighter fluid on it or some sort of degreaser spray. Those are the substances which will behave

[Extrabroker]

The front lens cell is a sealed piece. The haze is usually within the sealed piece. Unless there is a method to unseal that piece, then there is no way to remove the haze.