August 28, 2014, 03:23:31 AM

Author Topic: Chalking on focus rings on L lenses  (Read 3277 times)


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Chalking on focus rings on L lenses
« on: January 11, 2013, 09:52:41 PM »
Can anyone tell me why some L lenses rubber rings chalk over while some do not and is there an easy fix??

Thks for commentary and suggestions about this phenomenon.  The white powder looking appearance on the rubberized rings of some L lenses is exactly what I'm talking about.  While I'm not paranoid about it, one would have to admit that while browsing sites such as ebay you encounter this condition frequently and given a choice of two equal lenses priced about the same and otherwise similar condition, you are apt to lean toward the one without this condition. Always looking to acquire L lenses but have avoided these in past.

While I don't have this problem on any of my lenses nor have I ever seen it on a new lens, I have often wondered what caused it and if there were any further underlying problems associated with it.  Apparently, based on responses this does not cause any other problems and it is not a mold based issue. Thks for responses
« Last Edit: January 12, 2013, 12:24:10 PM by canonmike »


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Re: Chalking on focus rings on L lenses
« Reply #1 on: January 12, 2013, 12:38:13 AM »
I'm assuming that you mean the white power on the black rubber?

If the lens is new,  it's typically a form of mold release so that the rubber in the die doesn't get stuck when it's cooled and ejected from the mold. Automated molding processes are supposed to eject a precise amount whereas human interacted molding is, well, human. Sometimes, they just spray too much. For the automated processes, sometimes the hopper gets low and the operator will dump in a fresh load causing some air in the line to eject a glob of powder.

If it's older, it's usually the rubber reacting to atmospheric components. "Drying out" as you may. The rubber contains some oils and as those outgas, the reaction provides the white residue. Car tires do it, just not as white.

Either way, it's harmless. If you're paranoid, just wipe it off with a damp towel and add some "Tire Shine" to it. In the summer, I'll actually add some billard chalk to my 1Ds3's grip rubber so that it doesn't get slippery with could always use rosin too...then again, a lot of "tire-g" and you'll be bling'ing.
« Last Edit: January 12, 2013, 12:41:21 AM by docholliday »


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Re: Chalking on focus rings on L lenses
« Reply #2 on: January 12, 2013, 03:05:09 AM »
I had this happen on a old 70-200L f4 non IS lens.  It started getting white.  I cleaned it and then put on some of this stuff:

Worked like a charm, looks like new.  Like the other person said, it's just the rubber drying out.