Samyang 10mm f/2.8 - powdery focus ring?

[Crosswind]

My Samyang 10mm arrived a few days ago and after unboxing the first one, I had to send it back because Amazon delivered it to me with the wrong mount (for Sony E) instead of Canon EOS. What I noticed though, was that the focus ring had some sort of white/greyish powder on it - never seen something like this on any of my lenses (see picture). I thought this might be an outlier.

Then, shortly after they quickly managed to send me another one - this time it was for Canon EOS like I have ordered it. I've tested the lens and it isn't decentered, but also has this kind of powdery focus ring. What is that? Is it some sort of protection for the rubber part??

Anyways, I gently tried to remove the "powder" (or whatever that is) with an eyeglass cleaning tissue and other utensils, but it is very persistent and hard to remove. At some point it got better (cleaner), but I cannot fully remove it. The lens seems to be brand new and not used (no dust on lenses, no scratches, superb optical performance, undamaged packaging) - so this white coating must be something intentionally applied by Samyang in-factory. Maybe someone can explain it to me.

 

[siegsAR]

Might be some sort of rubber protection.

I remembered way way back when I had stacks of rubber bands, I put lots of talcum powder to prevent the rubber from becoming brittle. Everybody did it but no one really knows why. ;D

 

[Crosswind]

Then I'm hoping it's asbestos-free talcum powder!

 

[Mt Spokane Photography]

Its a common issue that occasionally shows up as it has for the past 40 years. Their are some components in the rubber that oxidize into a white powder. Its difficult to get totally clean, Getting a replacement is easier, but lots of elbow grease can work.

There are lots of theories as to what causes it. Oils, skin lotions, probably other common things may promote it.

http://www.bing.com/search?q=what+causes+white+rubber+on+lens+ring+&qs=n&form=QBRE&sp=-1&pq=what+causes+white+rubber+on+lens+ring+&sc=0-38&sk=&cvid=E797F283B8894B25B3556597205604C8

 

[Crosswind]

Thanks for pointing that out mt.spokane. As long as the focus ring works and doesn't fall apart, I'm fine with this.

Giving the lens back is out of question in my case, because apparently I got super-lucky to get one of the better copies (I've seen worse)! This thing is (for the most part) up to Canon L levels in terms of optical performance... (didn't expect that) and the focus ring is even smoother and more damped than the one of my 100L macro or 8-15L fisheye. I got it new for only 380 EUR and it seems to be the perfect filler between my fishy and the 24mm.

Btw. I think if the white layer is actually an oxidation process, then that could also come from a very long period of storage in not so perfect conditions. Though I've never seen it on any of my other lenses.

 

[Crosswind]

Some say it could also be fungus, but I don't believe so.

Now after I've used a regular cotton swab soaked with a bit of water and mild soap to carefully clean the focus ring surface, I could remove most of the "mess" (see picture). Then I thoroughly wiped it off with a rough towel. Worked pretty well. I think that's quite a difference now.

Btw. I can only recommend the lens to anyone who's interested in a relatively fast UWA for APS-C bodies. If you're lucky to get a good copy...

 

[Mt Spokane Photography]

A toothbrush is another good tool for getting into the cracks. Those rubber bands are one of the parts that Canon outsources, and occasionally, they have put too much of a ingredient in the rubber that makes the milky powder.

You do not have to send the lens back, if it happens, just call Canon and ask them to send you another rubber band. Thats all they are, get a small tool under one edge, and stretch it as you pull it off.