Loose Focus ring assembly

Turn the grey ring around the lens (where the light comes from) until the image is sharp.

check for PDF file online (how to assemble lens). Its free. If can't - get it on ebay.com for $5. Use it to open it and fix it . (Usually its easy) Or pay for the same work $200 at ant repair place :0)

What I would try to do is, loosen the screw so its not stiff to adjust, adjust the lens to the right position then tighten up the screw again. Hopefully this should work for you!!

The problem usually comes about when the focussing ring comes loose. Step 1 remove the 1.front round name ring 2. filter ring. this will expose three screws that hole the focus ring in place. reset the focussing to infinity on your viewfinder then set the ring to the infinity mark and retighten. If the helicoid has come apart then take the mount ring out, aperture ring out, and remove the two focus guides. turn the core out, set the fine thread back until it is almost against the ring directly behind it. make sure that it has at least one and one half turns. then engage the helicoid back. refit the focussing core into the lens and refit the two guides.reassemble the lens and revert to step one to reset the lens.

Hi, not sure if you still have this issue. I have just decided to look into it again, as I had a lot of focus problems with my Sigma 70-200mm HSM lens. Since there is no Sigma support here in Beijing, I took a look - and fixed it.

Here is what I did: On the front of the lens barrel is the rubberised focus ring. This can be removed (gently ply it away from the barrel by sticking a flat bit (or plastic letter opener) between the barrel and the rubber grip. It will come not entirely loose, so you need to work your way around the lens. Keep doing that until you moved it about half way forward. At this point two fixing screws become accessible on the barrel below.

In my case, one of the screws had come loose and that blocked the focus ring from turning, as the screw was blocking rotation in the access hole on the barrel.

Hope this helps others. Simple to fix, if you know how.

Inside the lens assembly is the focusing ring. When dirt, dust, lint, or sand work their way inside it can jam the circular geared movement necessary to focus the camera. The ring has two electromagnets on it, controlled by signals and feedback from the main board, to achieve focusing. To try to fix this, try to spray some compressed air into the lens assembly, holding the camera upside down. If that doesn't help, try different points around the lens. After trying that, you can try to bump the camera slightly, to try and dislodge a stubborn jam. sometimes the ring has sprung off its track, and you can reseat it by gently knocking it back into place. Hold the camera with the lens facing up when you do this. Otherwise, it's not a cheap fix, so get an estimate before you have it serviced. You can do it yourself, if you're inclined, and there are a lot of videos and information on YouTube. Good luck, and hope this helps.

Am having the same problem. I fixed it once but can't remember how I did it. I think there are screws under the mounting ring -which has four screws itself. Then, I think under the green computer board, there are other screws that should be tightened... I will look at mine tomorrow and come back here to report.

The USM focus works by applying pressure to a set of rollers. That pressure is achieved with a large diameter spring washer. It is held in place by another large diameter flat washer that on assembly is rotated 60 degrees to lock it in place. If the lock washer has moved due to mechanical movement (ie rapid manual movement of the focus ring) it could unlock and then all pressure to the USM motor parts and rollers is lost giving the loose feel you mentioned.

You will need to dissassemble the rear of the lens to see the USM motor parts, rollers and locking ring to reattach it. Follow the links at my pbase gallery to see the dissasembly. When I took my lens apart the focus and USM motor went all loose and I wondered how could it work ever!!!. The locking ring was off which sounds just like your fault. http://www.pbase.com/barry_2718/efs1785mm I also have a flex cable cracked which is a much harder fix. Take careful note of the parts (mark then with a felt marking carefully) to achieve a reassembly exactly as removed.

hi sounds like the screw that holds the ccd is gone but its inside you say it all works good....? put a SMALL!!! drop of "superglue" (3 sec glue) it will hold nice good luck

hi sounds like the screw that holds the ccd is gone but its inside you say it all works good....? put a SMALL!!! drop of "superglue" it will hold nice good luck