08-27-2015, 02:43 PM
Hi guys,
While we read reviews of posts of wonderful and maybe not so wonderful and exotic glass at equally exotic prices, out of the corner of my eye I could see my ever diminishing pile of pennies after the purchase of my Tamron 150-600mm and it's counterpart Nikon D750. I have one other FF lens the Nikon AF-S 70-300mm purchased cheaply because of sticking AF motor and a VR system which only kicks in after ten seconds and does not float the elements in stand by mode. A starting FL of 70mm is somewhat limiting....
Time to dig out some bargains!
I have had my eye on several AF-D 20mm F2.8 lenses popping up in the small adds here in France "The Bon Coin" a sort of buy now local ebay. I spotted one which claimed it had a couple of slight marks on the coating on the rear element for 250 euros, I sent an email offering 150 euros, in the mean time an add for a Sigma aspherical 28-70mm F2.8 EX screw-drive appeared for 80 euros, I telephoned and the guy said,
"it's just the manual focus ring which is a little stiff in places"
I decided to take the risk!
While the Sigma was en route, the Nikon lens man sent me some photos of the rear element, taken with a D810 the pic was testimony to it's resolution capabilities and the marks on the rear element was clear for all to see. I payed him by paypal.
The Sigma turned up and I could feel the focus ring was dodgy, I took a few picks and it didn't take long to ascertain it was nastily decentered.
As is my craziness, it was on the bench in bits within ten minutes, digging my way in I found the problem, the circular gear molded into the inner circumference of the lens barrel was in a poor state and bits of teeth were wedged in between other teeth giving the whole shebang an awful feel. This lens has a bad design of a rotating focus ring that occupies half of the width of the lens barrel, it takes a concentrated effort not to touch it, and that's what had happened to the previous owner and it damaged the teeth. I carefully cleaned it. In spite of the damage it still worked fine.
Now for the de-centerering, teabag boxes have very average optical properties but are very good for making shims, one thickness under on side of the bayonet and then a few test shots @ 28mm at F2.8, it was better, a second shim and Ah! that's pretty good.................
I preferred that the centering was good at the wide end and would take pot luck with the rest, so it was somewhat of a "eureka moment" when I found that 35/50/70 were all very well centered, excellent!..............
Well almost, now at 28mm the lens would not lock focus at infinity, the barrel was on the end stop. All to pieces again to find the adjustment, there isn't one as the stop is part of the barrel molding. I had a "Dremmel moment" and the job was done, back together with the obligatory ten minutes on my knees searching for dropped screws and cursing life the universe and everything.
On the Nikon it went and infinity focus was now a breeze. While I was destressing and regaining a natural heart rhythm, the phone rang, the Nikon 20mm had arrived.
I looked at the rear element it looked fine to me, whatever marks it had could only be revealed by a 1:1 macro on a D810 blown up to a 100%, off with Sigma and on with the Nikon. *
The visions of stripping down the Nikon together with a range of problems vapourised into thin air, "blinkin heck, I've got a good'n"
Was it worth the risk, buying two faulty lenses?............ I feel I was more than lucky that the gear teeth were still servicable and that two bits of tea bag box did better than Sigma did with all their laser lens alignment equipment at their disposal! Well now I have two F2.8 FF lenses that produce sharp photos for 230 euros, it's easy to say it was, but there were moments when I doubted my own sanity!
My current Nikon mount FF lens range and cost:
AFS 70-300 VRII 80 euros.
Tamron 150-600 new. 932 euros
Nikon AF-D 20mm F2.8 150 euros
Sigma 28-70 mm F2.8 80 euros.
BTW. I had repaired the 70-300 Nikons AF motor, but dare not go in to the VR system, unless one of you guys can shine a little light on the subject.
https://www.flickr.com/photos/124690178@N08/
While we read reviews of posts of wonderful and maybe not so wonderful and exotic glass at equally exotic prices, out of the corner of my eye I could see my ever diminishing pile of pennies after the purchase of my Tamron 150-600mm and it's counterpart Nikon D750. I have one other FF lens the Nikon AF-S 70-300mm purchased cheaply because of sticking AF motor and a VR system which only kicks in after ten seconds and does not float the elements in stand by mode. A starting FL of 70mm is somewhat limiting....
Time to dig out some bargains!
I have had my eye on several AF-D 20mm F2.8 lenses popping up in the small adds here in France "The Bon Coin" a sort of buy now local ebay. I spotted one which claimed it had a couple of slight marks on the coating on the rear element for 250 euros, I sent an email offering 150 euros, in the mean time an add for a Sigma aspherical 28-70mm F2.8 EX screw-drive appeared for 80 euros, I telephoned and the guy said,
"it's just the manual focus ring which is a little stiff in places"
I decided to take the risk!
While the Sigma was en route, the Nikon lens man sent me some photos of the rear element, taken with a D810 the pic was testimony to it's resolution capabilities and the marks on the rear element was clear for all to see. I payed him by paypal.
The Sigma turned up and I could feel the focus ring was dodgy, I took a few picks and it didn't take long to ascertain it was nastily decentered.
As is my craziness, it was on the bench in bits within ten minutes, digging my way in I found the problem, the circular gear molded into the inner circumference of the lens barrel was in a poor state and bits of teeth were wedged in between other teeth giving the whole shebang an awful feel. This lens has a bad design of a rotating focus ring that occupies half of the width of the lens barrel, it takes a concentrated effort not to touch it, and that's what had happened to the previous owner and it damaged the teeth. I carefully cleaned it. In spite of the damage it still worked fine.
Now for the de-centerering, teabag boxes have very average optical properties but are very good for making shims, one thickness under on side of the bayonet and then a few test shots @ 28mm at F2.8, it was better, a second shim and Ah! that's pretty good.................
I preferred that the centering was good at the wide end and would take pot luck with the rest, so it was somewhat of a "eureka moment" when I found that 35/50/70 were all very well centered, excellent!..............
Well almost, now at 28mm the lens would not lock focus at infinity, the barrel was on the end stop. All to pieces again to find the adjustment, there isn't one as the stop is part of the barrel molding. I had a "Dremmel moment" and the job was done, back together with the obligatory ten minutes on my knees searching for dropped screws and cursing life the universe and everything.
On the Nikon it went and infinity focus was now a breeze. While I was destressing and regaining a natural heart rhythm, the phone rang, the Nikon 20mm had arrived.
I looked at the rear element it looked fine to me, whatever marks it had could only be revealed by a 1:1 macro on a D810 blown up to a 100%, off with Sigma and on with the Nikon. *
The visions of stripping down the Nikon together with a range of problems vapourised into thin air, "blinkin heck, I've got a good'n"
Was it worth the risk, buying two faulty lenses?............ I feel I was more than lucky that the gear teeth were still servicable and that two bits of tea bag box did better than Sigma did with all their laser lens alignment equipment at their disposal! Well now I have two F2.8 FF lenses that produce sharp photos for 230 euros, it's easy to say it was, but there were moments when I doubted my own sanity!
My current Nikon mount FF lens range and cost:
AFS 70-300 VRII 80 euros.
Tamron 150-600 new. 932 euros
Nikon AF-D 20mm F2.8 150 euros
Sigma 28-70 mm F2.8 80 euros.
BTW. I had repaired the 70-300 Nikons AF motor, but dare not go in to the VR system, unless one of you guys can shine a little light on the subject.
https://www.flickr.com/photos/124690178@N08/