Nikon 50mm f1.2 problem focusing at infinity...

<p>Greetings All,<br>

I recently purchased this lens used and immediately fell in love with the build. I've discovered however it doesn't focus at infinity - falling short of realizing perfect focus (in other words, it doesn't rack past inifinity, it stops short) - and am trying to determine if its a problem with this copy - or an attribute of the lens. I've tried it on a couple of F2's, my F6 and D3s all with similar results. Does anyone else shoot this lens and have a similar issue trying to focus at infinity - or did I get a lemon? Any input greatly appreciated.</p>

<p><em>..in other words, it doesn't rack past inifinity, it stops short.. - </em>Not sure if I read you well; if it stops before reaching infinity, then something sure isn't good. It should however not go beyond infinity - it has a hard stop so it won't rack past infinity. </p>

<p>When the barrel stops rotating the infinity symbol is aligned with the black dot. The image in the viewfinder is however still out of focus.</p>

<p>What is the maximum focusing distance in the field, 5 meters or 30 m?</p>

 

<p>It's 5 meters/20 ft.<br>

For comparison sake, my 50mm 1,4D is 3 Meters/20ft.<br>

<img src="http://www.johnbcrane.com/img/s1/v47/p1914118635-6.jpg" alt="" /></p>

 

<p>I have never heard of this problem before for one of Nikon's most famous lenses. My copy focuses to infinity with no problems. I suspect your lens has been taken apart for servicing and been incorrectly assembled. Take it back to where you purchased it and ask for it to be corrected.</p>

<blockquote>

<p>"When the barrel stops rotating the infinity symbol is aligned with the black dot."<br>

-<br>

"I suspect your lens has been taken apart for servicing and been incorrectly assembled."</p>

</blockquote>

<p>Not incorrectly assembled. More than likely just not adjusted correctly for infinity focus, or else the adjustment has slipped. The focusing barrel on this lens will *always* stop with the dot and infinity symbol perfectly aligned, just as it always stops at the exact same location at the minimum end of the focusing range, as there are hard mechanical stops machined on the underside of the focusing ring and the underlying main lens barrel.</p>

<p>This lens uses a split focusing ring and the front half, which is attached to the focusing helicoid, can be adjusted relative to the fixed infinity stop of the rear half. It is a simple and quick adjustment for any qualified technician familiar with Nikon AiS lenses.</p>

<p>You might be shocked if you knew the "high tech" method employed to adjust infinity focus on this (and others) expensive and precisely machined Nikon AiS lenses. :)</p>

<p>The AiS Nikkor 50mm f/1.2 in all her beautiful, finely machined mechanical glory.</p>

<p>Let me know if you want to see a detailed photo of the "Nikon infinity adjustment securing mechanism". ;-) :-)</p><div></div>

<blockquote>

<p>It is a simple and quick adjustment for any qualified technician familiar with Nikon AiS lenses.</p>

</blockquote>

<p>Many thanks Michael - and thanks to Ross, Kari and Wouter for weighing in as well. This is what I was hoping. Though simple to the trained tech, I'll avoid the slight temptation to tackle it myself and send it in for proper servicing. The lens is worth it, gorgeous. The build is what drew me in but really enjoy the size and smooth motion of the oversized focus ring. But if it doesn't focus at infinity it's all but useless to me - which come to think of it probably explains why I got such a good deal on it. I haven't been terribly disappointed in the image quality - but can only look forward with excitement to a properly functioning lens.Thanks again.</p>

<blockquote>

<p>Let me know if you want to see a detailed photo of the "Nikon infinity adjustment securing mechanism". ;-) :-)</p>

</blockquote>

<p>Yes, please... Is this something that could be done at home by an untrained guy handy with small, delicate things?</p>

<p>As I said, you might be shocked and/or surprised. ;-) :)</p>

<p>Here is the "part", located under the rubber grip, that is used to adjust the position of the front half of the focusing ring (and thus the focusing extension) relative to the rear half with fixed focusing stops...</p><div></div>

<p>Some people set infinity using a target closer than 5000 feet <strong>assuming </strong>that the lens will be used stopped down 2 or more stops from wide open and that DOF will carry infinity.<br>

Your lens may have been set under such an assumption. </p>

<p>I used google maps for my location and the scale to find the 1 mile (5280 fee) radius from my window/porch to find what is usable. </p>

<blockquote>

<p>Some people set infinity using a target closer than 5000 feet <strong>assuming </strong>that the lens will be used stopped down 2 or more stops from wide open and that DOF will carry infinity.<br />Your lens may have been set under such an assumption.</p>

</blockquote>

<p>Thanks Charles, this is a good thought. When I tested the lens on the digital starting at ƒ1,2 and progressing to ƒ16 the images did sharpen up around ƒ8, optimizing between ƒ11 and ƒ16. Just the same - it's a little disconcerting to have the image blurry in the viewfinder, hoping it'll actually 'appear' sharp in the print. If it's a simple adjustment by a factory trained tech I'll have it adjusted to be sharp in the viewfinder - unless there's an advantage to the infinity setting you mention above.</p>

<p>I'm with you, I want my lens surgical scalpel sharp at their marked distance wide open.</p>

<p>Michael R. Freeman:<br>

Is older 55mm 1.2 AI lens fixed same way - using tape?</p>

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<p><em>"Is older 55mm 1.2 AI lens ..."</em></p>

</blockquote>

<p>I have not worked on the Ai 55/1.2, nor do I have a parts diagram for this lens, but my guess from looking at the focusing ring construction (removable nosepiece) would be that no, it does not use tape to secure a split focusing ring. Most small Ai lenses have a significantly different arrangement for focus stops compared to their later AiS successors.</p><div></div>

<p>If a lens is dropped and some elements become a little misaligned, this can cause the infinity focus to be off. But it can also be the infinity stop. You should take it to a qualified repairman.</p>