Nikkor 28mm f/2.8 AI-S - loosen front element

I have bought Nikkor 28mm f/2.8 ai-s CRC lens, which is said to be the best 28mm

Nikkor. It is in perfect condition ? looks as nobody has used it before. After

some playing with the new lens I realized, that I cannot focus to infinity. I

was able to focus only from 0.2m to 1m (0.7ft to 3ft). It got jammed on 0.5m.

After more detailed inspection, I found out that the front element is loose.

I?ve screwed it up and now it works well. I can now focus the whole range. Do

you think it?s gonna be all right and the lens is OK? Or is there anything

terribly wrong whit it?

 

Jirka

Hi Jiri, if it works OK now I bet everything is fine. When stuff gets shipped all over the world it gets rattled around a bit. I bet shipping vibration just loosened it a bit. Check it every now and then to make sure it's stays tight and you'll be OK.

If you have the time, shoot a series of test shots with it...it's boring and tedious, but it's the

only way to conclusively find out if it's OK. Pick maybe 4 focus distances: maybe infinity, 8ft,

3ft, and 1ft. Shoot each wide open, 1 stop down, 2 stops down, etc. WRITE DOWN ALL THE

SHOTS and the particulars of each. Tripod to eliminate camera shake. Shots should have

the same degree of sharpness top and bottom, side to side...if it's soft on the left but not on

the right, a lens element could be misaligned, etc. If your sample is like mine, the lens is

better at the wider stops(2.8,4,5.6) than it is at f/11and f/16. Good luck!

Hi Keith, when I am focusing the front element is rotating. Is it normal? My 50mm doesn't has this behavior.

 

Thanks, Jirka

"... when I am focusing the front element is rotating. Is it normal?"

 

No it is not. Something is obviously very wrong with this lens. As far as I am aware NONE of the Nikon AI/AIS primes, including those with CRC like the 28/2.8, rotate the front element when focusing. It should move in and out, but the rotation should remain fixed.

When focusing, front element moves in and out and it also rotates. Could some owner of this lens please approve that the front element on his/hers 28/2.8 ai-s does not rotate? Thanks.

All of the Nikon AIS primes have a slider(s) which rides in a slot machined in the rear portion of the lens barrel when the lens is focused (red arrows in attached photo I think). As the element group(s) move forward and back as the focusing ring is rotated, the slider keeps the front element from rotating.

 

I'm no repairman, but I think your lens needs disassembly and repair. If your front element is rotating, this piece is either broken or has come loose. Whatever the cause, something ain't right! :-(<div></div>

On both of my 28mm f2 the front element turns with focus, the 28/2 has the CRC with the

front rather than the back set of elements as is the case with the 35/1.4 and 24/2.8. As the

lens is focused an arm moves the front most set on a helicoid at a different pitch, giving the

CRC. I am not totally sure with the 28/2.8 AIS but it may be the CRC is front moving as well.

The loose element is not good though. But, if you tightend it and it is now sharp, you may

have fixed it.

Christian - you are right about the 28/2.8 (Bjorn Rorslett's evaluation of the 28/2.8 indicates that the CRC is via the front group, as is the 28/2). It's the one focal length I have not used in a Nikkor, and my CRC experience is limited to the 24/2.8 and 35/1.4. Thanks for the "education". :-)

 

Looking at the diagrams for both the 28/2 and 28/2.8, they look to have a similar construction with a cam/arm as part of the front group assembly (1K610-140-1 in the 28/2.8 diagram).

 

Nevertheless, I would be concerned about the initial focusing "jam" and loose front element. I can't see how any shipping vibration would be that significant to cause the problem if the lens were assembled properly when it was shipped.

Contrary to common belief, the front element of this Nikkor 28mm f/2.8 AIS does rotate upon focusing. What stays put is the filter mount, and the first mount ring with the lens spec engravings. I only noticed this when there was a thumbprint on mine's front element. I'll try to post a video clip on youtube so that you can see for yourself, but I'm not sure do I want to put a new thumbprint on the front element ...

 

What concerns me is the loosened front element in the first place. I'm not sure am I helping, but the fastest turnaround is to test shoot with a Canon 5D or 1Ds with a mount adaptor, and check for sharpness with blow up images on a good display.

Jiri,

 

I've got one (amazingly sharp) and the front element rotates (as last poster commented, filter

seat is fixed though).

 

mike

I have taken couple photos with my friend's Nikon D80. Unluckily I did not write down the aperture value. Anyway, could I know your opinion about sharpness of those two photos?<br />

<a href="http://www.fi.muni.cz/~xmatela/dsc_3450.jpg">first pic</a><br />

<a href="http://www.fi.muni.cz/~xmatela/dsc_3453.jpg">second pic</a><br /><br />

Jirka

I'd say the second photo is typically sharp for this lens at wide aperture, at the center. The first one seems to be in focus alright, but is not sharp.

 

The reason to pick those 2 Canon bodies for testing is because both are 135 full frame. Yes you can see how your lens performs with Nikon D bodies, but only at the center. Of course you can shoot film for full coverage testing, but you need more subsequent work to see for it.

yeah, I agree with Roland that the 2nd photo is more typical of the sharpness. The 1st one,

though, I am not sure it is in focus, though.

I've been getting the best results around F/5.6 - F/8, with careful focusing and tripod. I

like mine very much.

 

Try and take a few more pics, at different apertures, on a tripod if you can, and under

different lighting conditions. Also, shoot a larger variety of subjects (like, some flowers,

buildings, pets, etc) - and then I will be able to tell you more about how it compares to

mine.

 

As soon as I figure out how, I could post a couple of pics, too.

 

mike

Roland, I understand the reason but I have not this possibility by now. But thanks for suggestion, I did not know there is option like that. I will shoot a color film and will scan it -- by now, this the fastest way how can I perform some test of this lens.

 

Mike, it would be great to have some pics to compare with.

Jirka

 

 

Please have a look at my old portfolio on pbase :

 

http://www.pbase.com/roland_l

 

There are 3 photos taken by the Nikkor 28/2.8 AIS in each of the first two b/w galleries (with brief description below the pictures ...). May not be in the best size to demonstrate sharpness, but they show what this lens can do.

 

And we can forget using the youtube -- I have no way to get enough contrast to show the rotating front element. Nevermind, that's not the point :}

On digtal, my copy this lens is extremely sharp close up and shows decent quality near infinity, also at f/2.8. However due to slight field curvature, I suspect edges might be a bit weaker at infinity on full 35mm format. Here is a gallery with some test images with D200, including some downloadable 100% crops:

http://otoien.zenfolio.com/p993254891/

 

I had the problem with the front element coming loose with my AF 20mm (causing very blurred edges). First time the local repair shop used a special friction based tool to screw it back in. Next time I just used my finger tips. I was surprised to learn from this thread that the 28mm also has a rotating front element, could hardly see it with a clean front element. There is much less edge to grab on to than on the 20mm.

FWIW, I have owned 2 samples of the 20 mm AIS f2,8 lens and in both(!) the front optical assembly was loose and tended to become unscrewed when focusing. The lens has CRC. Could be tightened with a rubber tip and I never bothered repairing it.

 

Karl Johan

Jiri, Did you get your problem solved? I have exactly the same lens and today it seems like same problem occured, cannot focus beyond

0.4 meter. Is your lens functioning properly now? Did you repair it yourself?