Repairing a Sigma 70-210 f/2.8

I have conquered Mount ZEN. Took much work but I have removed and cleaned the slightly foggy element from my Sigma 70-210 f2.8 Zen

History is written up on the fist page. I was having trouble getting consistent micro-focus correct images as the setting required seemed to jump between +9 and -9. That is a huge range. I found then that there was a little slop in the focus ring and even when focus was on, a slight wiggle of the barrel would throw it off. So, I decided to take the lens apart to see if I had a loose gear or something else causing the play. When taking the lens apart, I removed the front-inner cell, the one with the hazy element, as a group. This was done after removing the front ring from the inside, under the objective. Removing that ring exposes the screws that have to be removed to fully pull out the lens group. This ring is a friction-fit. To remove it, I had to use a plastic cap and a rubber ring (lens grip ring from an old lens) and twist off the ring. Once the screws are out (only the 3 outer have to be removed), the lens group can be pulled out from the back. Once done, you have to remove the retaining ring from the BACK of the metal cell in the same fashion as the front ring but with a smaller cap or insert. You can then pull out the inner cell with the elements. There are 3 elements within- one at front and a doublet at back. To remove the elements itself was a challenge. There is no spanner inset for the front ring or rear. The font had locktite and I had to add a bit of nail polish remover to the gap between the threads top dissolve that (don't get any on the elements). Then, remove the front ring by applying a bit of pressure to the ring face (inside, not top and try to push counter-clockwise. BE CAREFUL not to scratch the element or jab yourself. BEFORE YOU REMOVE THE ELEMENTS, TAKE NOTE OF THEIR ORIENTATION. I put it all back together only to realize I had reversed the front element and had to start over.

Cleaned up the haze and lens works great BUT still that play in focus...will have to be careful on shoots. Took some test images. This is a very nice lens. Sharp and except for some vignetting at 2.8 and a bit of loss in the edges, which almost lenses suffer wide open, very good performer. I will try to post some images.

neilt3 wrote: Hi Osi . That's a sickner losing your phone with all the images on , I know how valuable they are for reference . .

My dear brother, if I lost only my phone with disassembled electronics, that's pretty painful; but it was my entire record of uncountable bookmarked pages,apps, settings, maybe over 19,000 images and thousands of video clipses on various subjects - most simply irreplaceable. I last backed up a full year previously. What I could get hardly represented 10% of what I lost. It feels worse than the death of a human being. I was willing to pay more than the value of the phone to get my information back, but when you misplace your phone in Nigeria, my brother, please forget it. The first thing they do is switch it off and throw away the SIM card and you can't contact them again. They're incapable of considering how vital information in a phone can be.

Edited by Osi - 30 May 2020 at 17:32

Hi Osi .
That's a sickner losing your phone with all the images on , I know how valuable they are for reference .

I've P.Med you my email address .

When I get chance I'll get them on Flickr and posted here so anyone doing a search can find them .
Hopefully they will be of help to others .
Cheers .

pegelli wrote: Osi wrote: The picture policy of this forum is an Achilles heel Judging by the amount of pictures posted on this forum on a daily basis it can't be that hard: see here for instructions Btw, good luck with the lens repairs

As explained in March , it's simple and free to start a Flickr account to post images on here , and other places .

I also offered to put the images on my Flickr site and post them in this thread to help others in the future .
Not been taken up on the offer though . Shame .

Osi wrote: I was still waiting for your link to produce a picture to no avail. The picture policy of this forum is an Achilles heel

I uploaded my images to an external hosting service (Imgur). Perhaps the forum software mangled the link for you? Try going to i.imgur(dot)com/waX8gFs.jpg

Yes, that's the one. It is difficult at first as when you tighten you grip, you may be squeezing it out of round. Try from a few angles. Normal direction (left).

When you get it off, the front barrel will come off (with the af version). The front element AND barrel underneath are held in place with tape. Do NOT take that tape off without first marking the front to rear sections or you will have difficulty aligning them back on.

Hi everyone. I did send the only picture I took of the completely disassembled lens to someone on here by e-mail but he said he was no longer going to attempt any further to work on it since his wasn't that bad. For the last poster's situation: indeed the focusing lens group is in the very front part. To access it, you will observe that the entire front section has a wider diameter than the focusing grip part. Take your hands from the very front of the lens all the way to the end of that part with same diameter. At the end of it, before the focusing grip is a ring deceptively placed there to lock the front barrel in place. Looking from the back of the lens, turn the ring in the normal anticlockwise direction and voila, the front barrel comes off going further forward. The very first front glass is attached to the rest of the lens by just a black tape! I'm sure you can figure out the rest or else my response will get too long and unwieldy. Please let me know how it went