Nikkor 1.2 Focusing Throw

LJSLATER · Jan 27, 2012

I currently own a 50mm f/1.2 AIS. I've seen pictures of the AIS version side-by-side with the older AI, and the latter (like most if not all AI and pre-AI lenses) seems to have a longer focusing throw, meaning the distances are more spread out, facilitating more accurate but slower focusing. Has anyone used both the AIS and AI versions? Is there a noticable difference in the ease of focusing accurately?

I ask because I get frustrated when trying to critically focus with my sample; the focusing ring doesn't feel precise enough. There's also a little bit of play when focusing back and forth, meaning when I switch directions, I can turn the focusing ring a fraction of a rotation before the helicoids move.

djacobox372 · Jan 27, 2012

Older ai lenses typically have more "throw," quicker focusing was one of the upgrades of the newer lenses.

As for the play, my 1.2 ais has no play--from my experience only well used lenses develop a bit of play.

Christiaan Phleger · Jan 28, 2012

I have and use an Ai version. Mine has had extensive use and has excessive play, I've adjusted what I can but some parts are just plain worn out and parts are NLA. But I stress, it took a long time and a lot of shooting for it to get this way. It was pretty worn when I got it and then I put 12 years of regular wedding shooting on it.
I have the shell of a Ais that I got of #bay ages ago for cheap, the throw is nicer, shorter. The size and weight of the elements in regards to the construction of the barrel assembly means that it puts pressure on parts when its used a lot, and if yours has that little wiggle then it most probably needs a bit of adjustment. I'd give it a good relube as well, the helicoid on the Ai is quite narrow and mine seems to work well with a bit more damping from the grease. Treat it well and it will last a really long time.

Christiaan Phleger · Jan 28, 2012

I have and use an Ai version. Mine has had extensive use and has excessive play, I've adjusted what I can but some parts are just plain worn out and parts are NLA. But I stress, it took a long time and a lot of shooting for it to get this way. It was pretty worn when I got it and then I put 12 years of regular wedding shooting on it.
I have the shell of a Ais that I got of #bay ages ago for cheap, the throw is nicer, shorter. The size and weight of the elements in regards to the construction of the barrel assembly means that it puts pressure on parts when its used a lot, and if yours has that little wiggle then it most probably needs a bit of adjustment. I'd give it a good relube as well, the helicoid on the Ai is quite narrow and mine seems to work well with a bit more damping from the grease. Treat it well and it will last a really long time.

LJSLATER · Jan 30, 2012

Thanks for the insight!

I also wonder if keeping the hood attached during transport has contributed to its wonkiness?

Christiaan Phleger · Jan 30, 2012

Well, it depends. Is it the hard hood or the rubber one?

Christiaan Phleger · Jan 30, 2012

I wouldn't say so. The filter thread ring attaches to the front barrel and generally does not put any excessive pressure on the helicoid assembly, which is further back in the barrel. I'm doing a mild cleaning and slight lube on my Ai, your post made me look over the lens.

LJSLATER · Jan 30, 2012

I use an HS-12.

I don't trust myself to make my own adjustments, but I'm not a heavy user so I think I'll just rock it the way it is for now. I have been known to be a bit of an "equipment hypochondriac" anyway. I'm also compulsive; I can't use split-prism focusing screens because I'll stand there all day focusing back and forth until the image is PERFECTLY aligned, unless I just fire a shot out of desperation.

Newt_on_Swings · Jan 30, 2012

I think that it has less to do with focus shift from a loose helicoid than it has to do with the fact that a 1.2 lens has very narrow dof wide open on anything other than at infinity.

If you are having focusing problems on smaller apertures then it could be something else, but at its widest, expect to have things not always perfect. Why not try a roll aimed at a tape measure or newspaper and see if it is lens, focusing screen, or user.

A simple upgrade in focusing screens will help a lot. I use a combination of G2, H2, and P screens for maximum brightness and speed on the 50 1.2. I have the AIS version that is very well dampened and smooth through out, probably one of the best feeling lenses I have.

JLP · Jan 30, 2012

My 50 1.2 Ais is about two years old and is rock solid but smooth. Have not used it much yet but have picked up 35mm again so it will see some use in the future. Great lens it is.

semi-ambivalent · Jan 30, 2012

LJ,

A bunch of years back I took apart a 105mm Nikkor-P to learn how it all works. In that lens the helicoids would turn 'within each other'. To keep the lens element assembly itself from turning when you turned the focusing ring there was a small brass projection attached to it that moved forward and backward in a slot machined in one of the helicoid's parts. This projection stopped the lens itself from rotating. This projection was split down the middle and had a counter sink headed screw screwed into the split. If this projection narrowed, or the slot it traveled in widened, through wear one could increase the width of the projection by screwing the screw a little deeper into the projection, thereby taking up the slop. Very clever. Perhaps your 1.2 has some slop that has to throw that projection to one side or the other of its slot and you're feeling that as a moment of free play when focusing. That 105 is #126380 and supposedly dates to 1959 or 1960 so your lens certainly has a different mechanism. But perhaps not that different.

Good luck

s-a

Christiaan Phleger · Jan 31, 2012

Yes, I call that the Key, in the Ais (I think, it could be different in the Ai version) it fits into a smaller slot than the larger brass that the older Nikkor-Auto 105mm P has. It sounds to me to be the key may need that adjustment. Over time there can be wear on that key, I should look at mine but I know if I do I'll probably take it apart and replace it. The slot the key linearly travels in can wear, that's why you can very precisely widen that key so there is no slop, Don't Overtighten, start with One Hour adjustment (only turn the slot the amount of one hour as if the screw face were a clock face) and test, if its still too sloppy add another hour. In addition, the two screws holding that key can develop some play, I think I recall on the Ais version it may be held by the red Nikon sealant. Now that I think of I am going to check out the internal build of my Ais shell. Stay tuned.

LJSLATER · Jan 31, 2012

Don't everyone take your lenses apart on my account!

This is very interesting though, I may just open my 1.2 to see what I can see; if I make a mess and can't get it back together, I'll have an excuse to get the AI version (unless my wife finds out what I've done

I should clarify what I meant in my original post, however. I'm not having trouble with my photos being out of focus. I'm merely picky, compulsive, and prone to anxiety :confused:

Christiaan Phleger · Jan 31, 2012

Just put my Ai back together, and yes, I DO NOT recommend anyone dismantle their fine Nikkor optic unless they have experience and are willing to take the risk.

The Ai version has the larger slot/guide assembly, with the sides of the slot adjustable, both sides being actual plates, held in place by 2 screws each.
I will check my AIs version.

LJSLATER · Jun 5, 2012

Hey guys, many questions:

Today I went to the optical lab next door to my office and borrowed some screwdrivers and a workbench. Starting at the lens mount, I took a deep breath and tore my way down to the aperture controls where I got stuck. I've removed the mount, aperture ring, and silver grip ring (one day I'll subscribe so I can post photos). Anyway, I see screws beneath the distance markings on the outer barrel, but I can't get to them. Also, the tab that screws to the aperture ring from inside has come disconnected from the aperture mechanism; how do you recouple it? Right now it's just rattling loose and even gets caught when I turn the focusing ring back and forth.

I was shocked by the click-stop mechanism, by the way; why isn't there a ball-bearing instead of a little tab? And I don't like that the aperture ring is plastic. The indents for the click-stops are really worn, which may give a clue as to how much use this lens has had.

There is a single, tiny screw right by the front element that I didn't try to remove. What does that do?

LJSLATER · Jun 5, 2012

Oops, edit: the inside of the aperture ring isn't plastic, it's just painted a matte black.

Christiaan Phleger · Jun 5, 2012

That little screw is what's needed to get thru to the front of the lens. Undo it and then twist that whole front barrel off, that holds the optical unit in place. Get that far and we'll see what to do next....

LJSLATER · Jun 5, 2012

Ok, so starting from the rear is the wrong way. Unfortunately, I can't find a flat-head that small, even in the lab (the guy fabricates lenses for eyeglasses and doesn't know about camera lenses--plus he's on vacation, which is why I'm using his junk). I'll have to go to the store for screwdrivers or order a set.

I was able to remove the front plate with the Nikkor logo though, I used the rubber focusing grip to twist it off by hand.

This is actually kind of fun, I should have done this a long time ago but I was afraid. Thanks for your help though, I really appreciate it.

Newt_on_Swings · Jun 6, 2012

If you have extras of a small screw driver that almost fits, you can file/grind down the sides until it does fit the right size. You have more guts than me with these more expensive optics and huge elements. best of luck.

Christiaan Phleger · Jun 6, 2012

Oh and the 'dimpled spring' aperture detent system is pretty good. The metal of that flat spring is harder than the anodized aluminum, so on lenses with *extreme* wear the inside of the ring wears first.

(see my blog post with the story about this lens.)
http://four-silver-atoms.com/2012/06/05/wear-and-tear-nikon-28mm-f1-8g-nikon-nikkor-28mm-f2-8-ais/

christiaan
four-silver-atoms.com

LJSLATER · Jun 6, 2012

I removed the microscopic set screw (and promptly dropped it on the carpet--note to self, unscrew screws over a tray with a magnet). I've taken the lens out of the shell and I can see two brass projections on opposite sides on the inside of the shell that go up and down in wide slots. When I turn the focusing ring, I can visually see quite a lot of play--the brass projections move laterally when they should only go up and down, correct?

Now I assume I need to remove the lens mount and aperture ring again.

What does the wide slotted screw near the front element supposed to do? Is it to calibrate infinity or something?

Christiaan Phleger · Jun 7, 2012

fftttt! yeah, those pesky tiny set screw. You need that, mostly, the optical group is held in by the barrel you just twisted off, that set screw keeps it tight so THAT doesn't loosen and move the optical group around OR out. Use a magnet on the carpet and see if that will pick it up, sometimes it works.

Ya don't have to to pull off the aperture ring if you don't want, the mount might need to come off so you can line up the aperture stop down lever with the slot on the optical unit when you Put It Back Together (which you Will, yes?).

The wide slotted takes off the front groups of elements in the Front Optical Block. Once you get the whole Optical Unit out you can see how the rear group can be removed. The helicoid barrel is next.

LJSLATER · Jun 7, 2012

Newt_on_Swings said:
If you have extras of a small screw driver that almost fits, you can file/grind down the sides until it does fit the right size. You have more guts than me with these more expensive optics and huge elements. best of luck.

This is what I ended up doing. The screwdriver I had was about 5/64", I think 3/64" or even 1/32" might be the right size(?). I don't know that I have guts, I'm probably just stupid. At least I'm not trying to grind the rear element to install a Dandelion Chip.

RidingWaves said:
fftttt! yeah, those pesky tiny set screw. You need that, mostly, the optical group is held in by the barrel you just twisted off, that set screw keeps it tight so THAT doesn't loosen and move the optical group around OR out. Use a magnet on the carpet and see if that will pick it up, sometimes it works.

Ya don't have to to pull off the aperture ring if you don't want, the mount might need to come off so you can line up the aperture stop down lever with the slot on the optical unit when you Put It Back Together (which you Will, yes?).

The wide slotted takes off the front groups of elements in the Front Optical Block. Once you get the whole Optical Unit out you can see how the rear group can be removed. The helicoid barrel is next.

Yes, I promise I will put it back together! Not just so I can use it (it's my second-most used lens), but out of respect, too. I'm trying to find the screw, I hope I'm not SOL. My coworkers are helping me look.

I'm taking care with the optical group. When it's removed, there's no way to attach caps, and there's not really any protection for the front or rear elements.

Christiaan Phleger · Jun 7, 2012

Just set it on its side and make sure it doesn't roll off the workbench. If you can't find the set screw don't worry, you can take one off another lens or you can even do without, just make sure you don't loosen that barrel when you unscrew a filter or hood.

LJSLATER · Jun 7, 2012

Oh, I didn't even think of that. I have a beat-up 200mm f/4 AIS of the same vintage that I never use. Sure enough, it has the same set screw, at least it looks the same. I actually called the Nikon USA Parts Dept today but I was on hold for about 20 minutes before I gave up.

Anyway, to get back to the focusing issue, I can't see any way to the adjust the the |_| -shaped focusing grooves or the brass protrusions. If the grooves are a tiny bit too wide and there is play, does this mean the grooves or brass "keys" are simply worn out?

I was going to set up a flickr account and take some close-up photos of the various interior components in case anyone is interested, but as it turns out, 108 proof Kentucky bourbon and black coffee on the side doesn't really mix with macro photography. Plus my D200's battery was dead when I tried to turn it on--I can't remember the last time I used it (it's my only digital camera, unless you count my iPhone, which I don't).

I might be becoming what Sover Wong refers to as the dreaded "cowboy".

Nikkor 1.2 Focusing Throw

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