[NomNamNom]

Hey guys, I just bought a 18-135mm from a local tent sale. After testing it at home,it seemed to do fine. After playing with quickshift and then letting it sit for a few hours, the barrel would get stuck at some points unless a little force is placed on it. The zoom also did not focus to distances of infinity if I were to be over 50mm.



I removed the lens and started to look over the barrel. I moved the focus ring and the zoom ring a few times and remounted. After a couple times of doing that, the lens will focus at infinity, but now the barrel will not zoom pass 100mm unless force is exerted. However, now when I force it pass 100, and audible click/clunk is felt and heard.



Any ideas what I could do? I've searched in hopes of having found someone with the same issues, but I didn't. Thanks in advance.

[stevebrot]

I hope you did not spend too much money

This is not normal behavior and the symptoms are typical of a lens that has been dropped or suffered some other form of physical abuse.


Steve

[NomNamNom]

I hope you did not spend too much money

This is not normal behavior and the symptoms are typical of a lens that has been dropped or suffered some other form of physical abuse.


Steve

Steve, I spent a little under $100USD. I was so giddy about how no one in the tent was remotely interested in Pentax, so that it gave me freedom of be the sole Pentaxian raiding goodies for myself.

I ended up forcing it to go over 100MM and hoped I wouldn't break it. It's not zooming out somewhat properly and still focusing right (I think..). However, after another close look, I've noticed a lot of scratch marks on the plastic shroud around the rear elements. Kind of feel very iffy about it and I am starting to lean on your take of physical abuse.

[adwb]

As Steve said I bet this one had been banged on something.
A lens can take a surprising amount of knocks than one day a insignificant knock on a door frame or something can distort the outer turning body and then it gets a stiff spot
I have a tamron f2.8 70-200 that will hand focus right down to the closest it will adjust to, but the auto focus stops short of that point by about 1/2 a foot, due to a hard to feel tight spot

[NomNamNom]

Well I suppose things have gotten a bit better. The lens is focusing well. The IQ is superb! Even the zoom is fully extending!!!

....although, this only is fine now that something has fallen out(!) after removing the lens and shaking it. I took it off again just to triple check it, then I heard rattling and saw some white spec bouncing about. I made it fall out and am wondering what it could possibly be? Possibilities of some more things clattering about in the future and damaging my camera, perhaps?

[FrankC]

If you were to take a zoom lens apart, you'd see a helicoid barrel. It's this barrel with a spiral groove (helicoid) in which a bearing sits. I would venture to guess that what fell out was a nylon bearing that was misaligned, causing the original binding problem at 88mm. I'm guessing that it'll be between $125 - $200 USD to have the lens repaired. If you're going to send it in, I'd inquire if you should send the body in too, so that the lens can be calibrated to the body.

[stevebrot]

I would venture to guess that what fell out was a nylon bearing

That is my thought as well, though the bearing looks to be in pretty good shape. That makes me wonder about the condition of the helicoid.


Steve

[NomNamNom]

If you were to take a zoom lens apart, you'd see a helicoid barrel. It's this barrel with a spiral groove (helicoid) in which a bearing sits. I would venture to guess that what fell out was a nylon bearing that was misaligned, causing the original binding problem at 88mm. I'm guessing that it'll be between $125 - $200 USD to have the lens repaired. If you're going to send it in, I'd inquire if you should send the body in too, so that the lens can be calibrated to the body.

Well then, that kind of makes me quite a bit uncomfortable. In your folks' opinion, do you think I can get away with continuing to use the lens as-is? Or is it like a ticking time bomb where the parts will one day rain into the body, thus causing harm to the sensor? I know it may be kind of hard to say since neither of us know its previous life with the previous owner, but you guys have been a great help thus far.

[FrankC]

I don't think you need to worry about that ever happening. I'm less skeptical, however, about having a part of the lens along with all of the elements slide off & smash onto the ground leaving a hollow tube mounted to your camera. Take this thought with a huge grain of salt since I'm not a technician nor have I ever taken a lens apart.