Nikkor 45mm f2.8 GN

[frank_yang]

Hi I recently bought a 45mm GN lens but found that the focusing

throw have a lot of play and when turn the focusing ring from end to

end the elements dosn't seem to move in & out in proportion with the

focusing throw. I bring it to my local camera repair shop and they

tried for one hour but cannot and does not know how to take the lens

apart? The shop told me they don't have a repair manul for this lens

and even Nikon USA does not repair the GN Nikkor anymore. Does

anyone out there can point me to a source that have experiance in

rpairing this lens? Its a late production model with Nikkor-C

coating and 765711 serial number.

 

Any help appreciated. A copy for a repair manual will be nice

[vivek iyer]

I had taken one of my samples apart for a clean. No problems for me (my sample, my risk!).

 

The C version is rarer (expensive). Be careful with trying to get it fixed. Try to disengage the GN pin and keep it that way. If it focuses properly and works alright as a lens, best to leave it AS IS.

[frank_yang]

Can you tell me how did you take the lens apart? from the front or back? My repair shope have unscrew all screws on the lens and nothing seem to move. My guess is to unscrew the front cone shape funnel ring but I can't get it to move without defacing the ring so I leave it for now unless I'm sure that the way to take the lens apart.

[Jerry_]

You might try a e-mail request to

 

 

 

www.nikon.com

 

 

 

in Japan. They may have a recommendation on a place to do a CLA on the lens.

[mike_grigsby]

Just curious: what makes the C version more rare? I have a non-C that I like very much. Thanks!

[vivek iyer]

"My repair shope have unscrew all screws on the lens and nothing seem to move."

 

Frank, This clearly shows that these folks are incapable of doing anything worthwhile. You take the focus mechanism apart from the back.

 

The "C"version was a late run. Purportedly made for one year before GN-Nikkor was discontinued. The origonal GN-Nikkor has a single coating. The "C"has NIC (or nikon integrated coating) which makes it less prone to flare.

[matthew_lin]

<p>I have taken apart several older non-Ai Nikkor lenses but I have never tried the 45mm GN. What you normally do is to remove the 3 to 5 screws on the focus ring and then remove the focus ring itself. Once you have the focus ring removed, you should see a few more chrome or brass screws which secure the optical group of the lens to a mechnical focusing unit. With this GN lens, things are slightly more complicated, because the focus is mechanically linked to the aperture. You should disengage the "tab" first before tying to remove the foucs ring, I think. If the going gets too tough, you can try Peter Smith who is one of the most experienced Nikon repairman in the USA for this type of equipment. He used to have a website but he now only operates a store in ebay. You can do a search and send him an e-mail.</p>

 

<p>As to which version is more valuable, well, I personally think the first version with 9 aperture blades is more interesting to collectors, altough the later versions are more useable. It really depends on what you are looking for.</p>

 

<p>For more information, you can check out my website below which has an article about this 45mm GN lens.</p>

 

The address is: <p> <a HREF = "http://www.matthewlin.com"> www.matthewlin.com </a> </p>

[dante_stella]

Don't take it apart. That is normal behavior; the lens group stops moving near infinity.

This is related to the hyperfocal behavior of the lens.

[scott_warn]

From your description, your lens IS working properly. The GN Nikkor does NOT have a focusing helicoid like a normal lens, it is focused by a cam similar to how a zoom lens works. The cam is used so that the focusing action can be "tuned" to match the movement of the aperture ring. That is also why the lens focuses in the "wrong" direction. As to your observation the the lens doesn't seem to move near infinity, that is all BECAUSE of the cam action. At long distances, the lens movement has to be reduced in order for it to track the aperture change with the distance. The result is that, at longer distances, the focusing ring has a lot of movement for a small change in the focus distance, IT IS COMPLETELY NORMAL.

 

Because the lens movement is controlled by a cam riding in a slot, any wear will result in a bit of "slop" in the focusing action. I have had mine since it was brand new and it has always had a bit of "slop". You get used to it after a while and that slop really doesn't cause any problems with the images.

 

Bottomline, if it aint broke, don't fix it, and your lens AINT BROKE. It is just "different" and you'll have to get used to it. If you can't adapt to the somewhat odd focusing, sell it and buy the newer "P" lens, it uses a standard focusing helicoid and will feel a lot more "normal".

 

BTW, the new "P" lens is on my "buy" list. It's a very similar formula to the original and being capable of electronically communicating with the new cameras is a real plus.

[duncan_wong]

disengage the "tab" first

 

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may I know how to do that ?