Originally posted by mgvh I don't know what all is involved with element separation, but it doesn't sound good. As long as I can take acceptable pics with the lens, I suppose it's okay, but what does this mean with respect to the life of the lens? Is going to get slowly worse or just fall apart suddenly some day. Mine is a macro lens, and I have no replacement for it, but I have to be able to count on it.
IIRC element separation (ES) results when lenses of a certain vintage, whose elements are adhered with certain cements, dry out. IIRC a pine(?) resin is used as glue, and the edges of the joined elements are sealed. But after some time the seals break down, air leaks in, and the glues dries, decomposes, no longer holds the elements together.
ES is not self-healing. It will only get worse. Over a period of about 6 months, I could see more and more bubbles (more separation) in the Kiron 24/2. IIRC it is hastened by physical shocks and dry climates. No, the lens won't suddenly die (unless you drop it), it'll just get sicker and sicker. For general photography, you could get away with calling it a "romantically soft" lens. For macro work where sharpness is vital, you're screwed.
I could be wrong about ES on your lens. It could be dust, although I've never seen such dust in a lens. One indication: If you leave the lens alone for a few months and more bubbles appear, it's probably ES.