Nikkor 300mm 1:4.5 manual, how to adjust infinity focus?

[Dero]

Hi

hard stop on focus adjust at infinity before focus achieved. Can this be adjusted? Lens focus great upto horizon.

 

[Kino]

Personally, I would suspect a petrified glob of lubricant impeding the helicoid from reaching infinity or that the lens was disassembled and not reassembled correctly.

I've had a number of Nikon optics apart and know that if you are not extremely careful in reassembly, you can very easily wind-up with a problem like not quite reaching infinity on focus.

I usually turn to Richard Haw's excellent site on disassembling and refurbishing Nikon lenses for information.

Repair: Nikkor-H 300mm f4.5 Auto

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richardhaw.com

(This may not be the exact lens you have, but it should be in the same family and instructive reading)

That being said, we see it is a lens he discourages beginners from tackling, so you might consider sending it into a repair shop to be disassembled, cleaned and re-lubed.

Quote: "I will not recommend this lens to beginners due to the fact that the glass is bigger and you will require special openers just to open some of the parts. These are mostly openers and spanners that are bigger than your average-sized ones and you may have to fabricate special ones yourself."

Of course, it may be less expensive to purchase a used, good condition replacement lens than have it serviced; that decision is up to you.

 

[Dero]

Thanks for the info Kino. I did previously look at that web site but he didn’t have my 300 on it. He has an exteriorly similar 200, so I looked at that guide.
but the fix was simple (?), under the rubber focus grip the are 6 jis screws in slots. These were in mid range, so I loosened them and twisted barrel to allow infinity +. Focusing on objects 1km now show up much better.

 

[Kino]

Sorry, I thought you said you could not obtain actual infinity focus.

Yes, if someone really cranks hard on the focus collar, it will slip out of alignment.

 

[reddesert]

When a focusing collar or similar lens part is held in place by set screws / grub screws, you can often tell where it was originally set by the indentations in the inner part. If you can take the collar off then you can see the indents, or if not, sometimes if you take the screws out then you can see through the holes to find where the original indents were, and if not sometimes you can find the indents by feel, loosening the screws and turning the collar until you feel them hit the original notch.

If someone cranked too hard on the collar and moved it away from the original position, you may be able to see the scratch marks. This can also happen if a few of the screws worked a little loose.

The real problem I find when trying to work on a lens is if the focus helicoid comes apart, it can be difficult or near-impossible to reassemble it correctly.