I recently bought a camera as parts, and it came with a Tokina SD 28-70mm 1:3.5-4.5 lens. This lens was in a bit of a state, and I already have a Canon 35-70mm FD mount zoom, but I felt like I had to at least try to repair it on principle, you know? The optics of the lens seemed fine, but the focus and zoom rings were both out of action. The focus ring moves the focusing element, but can also slip backward, lose contact with whatever holds the focusing element, and spin freely. The zoom ring was relatively stiff, though the rubber was loose and would easily slide around the ring. I tackled the zoom ring first because it seemed easier.
Prompted by this MFlenses post, I removed the zoom ring rubber and confirmed that the scotch tape holding the rings together was indeed the culprit. I still can’t believe that the fairly critical worky bits of this lens are basically held together with stationery (but this does seem to answer the poster’s question about whether this is how these Tokina lenses came from the factory). The scotch tape’s adhesive had degraded to the point that it was a fairly slimy lubricant and was doing very little to hold things in place. I removed the tape, and then removed its disassociated adhesive with a small amount of isopropyl alcohol on a cotton bud.
Because the zoom ring rubber had also stretched, applying fresh scotch tape wouldn’t have fully fixed the problem. I had been impressed by the stickiness of the self-adhesive craft foam I used to repair the Ricoh 500G, and thought that it might make a decent substitute. Since it came in a multicoloured pack, I also decided to follow this guy’s lead and have some fun. The lens has a red ring around the business end, so I used some red foam cut into a strip of the appropriate width with a rotary cutter. The foam sheets weren’t quite long enough to reach around the circumference, so I cut an extra piece to match and made sure it was on the bottom of the lens barrel when attached. I tested rotation at this point – it stuck well and the ring was easier to move. I then replaced the zoom ring rubber, which fit quite snugly over the top of the foam. I think, despite the colour of the foam not quite matching the red at the end of the lens, it matches the lens’s aesthetic quite well. And it is definitely easier (read: actually possible) to use the zoom ring now.
I wasn’t able to do the focus ring at the same time because it was night. I need to be able to focus at infinity to line the focus ring up to the front element correctly, and that’s much easier in daylight. The focus ring rubber isn’t as stretched so I doubt it will need the same foam treatment. However, if padding was required, I think I would do it with black foam so that it wouldn’t look too busy.