Repairing a Sigma 70-210 f/2.8

Rear group.... if I recall other similar lenses, 4 silver screws for mount, 3 small black ones for shroud, 2 slightly large black ones for contacts, rear cell should unscrew. They may have used locktite type products on the threads. Send a picture if you have one.

neilt3 wrote: beeton wrote: Rear group.... if I recall other similar lenses, 4 silver screws for mount, 3 small black ones for shroud, 2 slightly large black ones for contacts, rear cell should unscrew. They may have used locktite type products on the threads. Send a picture if you have one. I've no pictures to hand , that's if I took any . When I get chance I will dig the lens out and post some to i.d it , as well as stripping some of it down again to have another look at it . The rear lens group has haze , hopefully just a layer on the innermost parts that will clean up , and not between two cemented pieces .

God! How powerful the internet is. Well, I hope I'm doing this right and poster can see my message. Being an old lens, I didn't bother to check online for assistance but after two days battling this rear lens group, I decided to give it a try. Let me assure you I have 100% the same problem and SADLY, the haze is not accessible (at least yet) and that's why I'm here. The haze is between the two exposed sides of the very last set of elements and I've exhausted all the tricks I have trying to extract the elements from the housing to no avail. It looks like they're sealed together but I saw no tell tale signs of Balsam separation. The haze is so bad I could not convince myself it was made that way. It cuts as much as a third or half of the light through it! Anybody with any clue? I'm a very experienced and competent amateur self-taught repaired of these things and I got this far in the disassembly process only to get stuck here. Heeeeeeelp!

To post a photo you need to upload it to a hosting site such as Flickr .
Then copy and paste the BB code into your reply .

Thank you Neilt. So one has to join another online platform just to post a nondescript picture here. How great

Osi wrote: Thank you Neilt. So one has to join another online platform just to post a nondescript picture here. How great

Welcome to Dyxum Osi, I hope you will get your lens fixed.

And unfortunately this "free" site doesn't have the capability to store all the images shown here, cost and server size needed would be prohibitive. So you need one site for your images (there are plenty free ones) and then you'll get us for all the help the membership can provide here

I HAVE DONE IT! I came here for help, and now I'm the one who has provided the help! I feel glorious! Ok, I've taken the WHOLE lens apart only to discover I didn't have to. Right at the back of the lens there is an aluminum sealant to the very last lens element and it is the inner part of that group that gets hazy. I severely chipped some metal to succeed in this guesswork (informed as it was nevertheless). Just take the flattest, strongest metal you can find and pry from the inner edge of the outer reaches of the glass and pull the metal up and outward, going around as you do. Alternatively or in addition, stick the narrow strong metal inside the first gap (from middle) an try to pull up also. Don't tell me you won't scratch the metal because it's inevitable -- I don't think they made it to be removed. When you do that, the thin aluminium ring which acts to seal everything up would pop out, followed by an inner separator aluminum, and then the guilty element. THAT'S ALL! Ok, let me go now and see if the haze can be cleaned off. I feel very accomplished. My toughest project has now been carried out. I should add that I feel manual lenses are harder to dismantle than autofocus ones. That's my own experience from doing this thing on over twenty lenses. Cheers

It's good your getting it sorted .
A few photos would be extremely helpful as if it's the same lens of mine , I've still to dig them out to clean them up .