Thanks Bill That’s interesting. I’m sure I had the Tokina 28-70 2.8/2.8 at some point in the past, but memory starts to get hazy.
In the end I found a ‘spares or repair’ Nikkor AF-S 28-70/2.8 going cheap at a very good used gear retailer in London called MPB.com - I’ve used them before when buying high value broadcast equipment. The lens basically ‘wouldn’t focus past the 2m mark’. These AF-S lenses suffer similar problems with AF motors conking out, apparently. I’ve had my 17-35/2.8 apart in the past so ordered this one for 135GBP. I took it apart yesterday and sure enough, bingo. What happens is that the inner workings of the lens (eg the solid surrounding polycarbonate holding the lens groups in place) is surrounded by a hexagonal-shaped piece if thin aluminium which sits in between it and the outer metal surrounding lens casing that carries the zoom and focus rings. On both sides of the thin aluminium is glued various printed circuitry all the way around - and there’s plenty of it. Over time and handling, some of the glue starts to weaken and occasionally a wayward edge of plastic film type circuitry comes away from the aluminium - just enough to interfere with the spinning AF inner ring - actually it’s the bit you can see through the little ‘window’ on the exterior of the lens, displaying focal distances. This is similar on many lenses, including Pentax I believe. Of course, the more the bit of circuitry becomes interference fit, the more it interferes, until it basically gets caught and stops the AF motor being able to push this inner ring around and achieving focus. I’ve seen fixes on Youtube (search user ‘mikeno62’) where the glue on the weak bit is replaced. In my case, I just ripped all the circuitry out and tossed it in the bin!! I don’t need no stinking AF. Also de-clicked the aperture ring - one of the main reasons I sought this lens and one like it - manual aperture control. Plus the glass is uber sharp, great for HD video wide open. Probably more than you were expecting here :-) As you were Cot On 10 Jan 2023, at 22:31, Bill <[email protected]> wrote: I had the Tokina for a while. It was plenty sharp enough even wide open, but I was into shooting environmental portraits at the time and it had just enough barrel distortion to be upsetting, so I let it go. -- %(real_name)s Pentax-Discuss Mail List To unsubscribe send an email to [email protected] to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
