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Infinity focus is wrong in two Nikon lenses
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PostPosted: Mon Jul 14, 2014 11:31 pm    Post subject: Infinity focus is wrong in two Nikon lenses Reply with quote

Hi, all, newbie here.

I took two of my favorite lenses for CLA, and the @#$% shop put them back incorrectly, so that infinity focus is wrong.

In a Nikkor 50mm f/1.4 (AI), it was focusing past infinity and the focusing ring was misaligned. I was able to fix the misalignment of the ring, but I can't figure out how to realign the helicoid.

In a Nikkor-N 28mm f/2, the shop left a lot of front-to-back play in the focusing ring, and some rotational play as well. Also, the lens doesn't reach infinity focus.

I haven't disassembled the 28mm f/2 yet, but it sounds like they also misaligned the helicoid. I hope the play/looseness in the focusing ring is easy to fix; no idea what is causing it.

Is there a recommended way of re-screwing the helicoid to the inner and outer pieces, other than trial and error? I'm having a lot of trouble screwing it at all in the 50mm f/1.4; already managed to do it once, and it's not even in the right "slot" yet Sad

Thanks for any advice!

(Lest you think I'm a complete idiot, I managed to erroneously disassemble the diaphragm and had blades all over the place... put it back together after a little trial-and-error, and it turned out fine. But the helicoid is giving me fits) Smile


PostPosted: Mon Jul 14, 2014 11:33 pm    Post subject: Reply with quote

I forgot to mention - I don't trust the shop to put them back together properly if I bring the lenses to them again. The guy was pretty clueless when I showed him *in the camera* how infinity focus was off.


PostPosted: Mon Jul 14, 2014 11:53 pm    Post subject: Re: Infinity focus is wrong in two Nikon lenses Reply with quote

Welcome FedericoMenaQuintero

FedericoMenaQuintero wrote:
Is there a recommended way of re-screwing the helicoid to the inner and outer pieces, other than trial and error?


Other than using the alignment marks made during dis-assembly, I don't know, but if you find method for one lens it may repeat well in the others. Perhaps a lens was already CLA before; you might check for alignment marks. Remember you are lucky the lenses are not zooms. Smile


PostPosted: Tue Jul 15, 2014 12:25 am    Post subject: Re: Infinity focus is wrong in two Nikon lenses Reply with quote

visualopsins wrote:
Other than using the alignment marks made during dis-assembly, I don't know, but if you find method for one lens it may repeat well in the others. Perhaps a lens was already CLA before; you might check for alignment marks. Remember you are lucky the lenses are not zooms. Smile


Thanks, that's a good idea. I'll look for alignment marks tomorrow when sunlight is good Smile

I have no idea if these lenses had ever been disassembled before I took them to this crappy shop. I bought them used over 13 years ago, and other than gradual dirtification, they've performed very well.


PostPosted: Tue Jul 15, 2014 3:55 am    Post subject: Reply with quote

Make sure the floating elements(CRC) on Nikkor-N 28mm f/2 is working fine.


PostPosted: Tue Jul 15, 2014 1:12 pm    Post subject: Reply with quote

calvin83 wrote:
Make sure the floating elements(CRC) on Nikkor-N 28mm f/2 is working fine.


Hmm, how do I do this? Smile I haven't disassembled that lens yet, so I don't really know what to look for.


PostPosted: Tue Jul 15, 2014 2:40 pm    Post subject: Reply with quote

I don't know about old Nikkor lenses, but most makes have a way of adjusting the infinity setting. Usually, under the engraved ring
round the front element there are 3 screws which clamp the outer helicoil to the focussing ring. The procedure is to focus carefully on
infinity through the viewfinder, and then loosen these screws so that the ring can be rotated without moving the helicoil. Set the ring
against the infinity stop and tighten the screws. I hope this works for you.


PostPosted: Tue Jul 15, 2014 3:15 pm    Post subject: Reply with quote

FedericoMenaQuintero wrote:
calvin83 wrote:
Make sure the floating elements(CRC) on Nikkor-N 28mm f/2 is working fine.


Hmm, how do I do this? Smile I haven't disassembled that lens yet, so I don't really know what to look for.

The floating lens group(s) will have their own separate gearing allowing them move independently to the other lens elements. You will be able to discover them when you are disassembling the lens. This is all I know. Smile


PostPosted: Thu Jul 17, 2014 3:16 pm    Post subject: Re: Infinity focus is wrong in two Nikon lenses Reply with quote

FedericoMenaQuintero wrote:

In a Nikkor 50mm f/1.4 (AI), it was focusing past infinity and the focusing ring was misaligned. I was able to fix the misalignment of the ring, but I can't figure out how to realign the helicoid.


If it reaches infinity, all you need to do is set the infinity where you want it to be. The only reason to disassemble the helicoids would be if the lens could not reach infinity.