Nikkor 10.5mm f/2.8 - 62mm filter threads modified

[ARTUROARTISTA]

I already have the lens,

[Øivind Tøien]

The shaving conversion is not difficult, just make sure to use an aluminum soda can/sheets from a aluminum can to protect the optics, tape against dust intrusion, measure accurately and go slowly.

While I found a trick to force FX mode on the Z8 and set the aperture on the 10.5mm as posted here: https://nikongear.net/revival/index.php?topic=11224.msg209380#msg209380, I finally broke down and bought a cheap dumb adapter to dedicate to the 10.5mm. I liked the design better than the one in that link, price was $25 lower, but might need to add front/rear caps that do not come with it.  The F-mount fit is nice and tight, while the Z-mount side is looser than the FTZ II adapters I have, more the same resistance as mounting the 24-120mm. An Amazon review stated that it has a plastic Z-mount, but I am pretty sure mine is made of coated metal. The register distance seems OK. I was able to calibrate the aperture clicks to a mid range setting of about f/ 5.6-8. The ring has a dampened feeling to it, probably due to generous application of grease to provide the illusion of a precise mechanism.

[Erik Lund]

Very nicely done! Looks super nice
I like the soda can approach 

[Øivind Tøien]

Very nicely done! Looks super nice
I like the soda can approach 

Thanks Erik, much appreciated, especially coming from you. The first thing that came to my mind when I was searching for that soda can was the classical thread with Jacov and all the the soda cans, wondering if one of the cans in that collection would fit the 10.5 mm.  https://nikongear.net/revival/index.php?topic=66.msg252#msg252. Again thanks for putting me on the path to this conversion.

[Erik Lund]

He he, I often think of that image with the Can shower 
Thank you!

[toups]

Nice work all.  Thanks to this thread, I've been inspired to find a 10.5mm lens.  I managed to snag a used 10.5mm for a nice price.  It will arrive soon and will be under the Christmas tree for me to open later and be surprised or at least very thankful.

Since this is for use with a Nikon D610 and I already have a Nikon 16mm f/2.8 fisheye, the 10.5mm will be going under the knife to remove the petals for full frame use.

[toups]

While surfing the topic, I ran across two interesting sites and a copy of a service manual for the 10.5mm f/2.8 G lens.

The video I found had to do with adding helicoid grease to allow for smoother manual focusing.  Based on the feel of the manual focus, this sounded like a nice addition.  The video is at https://www.youtube.com/watch?v=LhCr8vdLzm4  Long story short, the author stripped the lens down further than I want to do to grease the helicoid.  Also, from the service manual I found it warns in bright red text:

Caution：
In case the rear lens group is detached, it is necessary to inspect the resolving power after assembly.
Therefore, if such an inspection cannot be made at service agencies, do NOT detach the rear lens group.

He went so far as to remove the rear elements, the aperture blade unit, and more, and split the front element group before removing it.  All in all, the video is missing some key steps such as when the hood was removed.  Also, probably much more may have been disassembled than needed to access the helicoids but that is not clear.

The second post relevant to trimming the hood is https://blog.captivephotons.com/cutting-the-nikon-10-5-fisheye/  The interesting point of this post is that the author detaches the screws holding the hood to manage to move the hood somewhat forward to cut the hood with the lens somewhat out of the way.  They thought maybe the hood could come off but couldn't see how.

Based on these three sources, it appears that the front element group can probably be unscrewed (assume but not sure) using the outer spanner wrench slots.  From the service manual it appears that may allow the hood to be removed by removing the screws as shown in the post sited.  What was not stated in the video but I implied from the things that were not shown was that the front lens group was difficult to remove and that may be why the front element was removed to allow some acetone to be used to loosen the assembly and they had to split the front element to access the threads.  Warning as was noted in the video acetone will ruin the plastic lens finish.

So two reasonable methods to cut the hood may be to
1) use a can to protect the lens.  (Probably still the simplest and safest if done with care.)
2) the front lens assembly can be removed by unscrewing and hood can be removed next by removing three screws hidden under the rubber focus ring to allow the hood to be cut while not on the lens.

Not sure if number 2 is feasible but certainly looks interesting.  (One of the comments implies that the front lens assembly is difficult to impossible to remove.)

While applying helicoid grease is tempting, in the spirit of "If it's not broke, don't fix it" the level of disassembly in the video is a step too far for me at this time.

[Øivind Tøien]

I recently noticed that my copy of the 10.5mm actually has a slightly loose front lens group that can be rotated just by the light force of cleaning with a fiber cloth. I tried to carefully tighten what looks like the retaining ring to no effect (it did not move and appeared tight). The performance does not seem to be affected and is still excellent on my Z8. Another note is that it for a long time has developed what I initially thought could be beginning separation, which is visible slightly below the center in the 3rd image in post #24. However after inspection of the optical diagram it appeared to my relief to be a shard or other anomaly at the back lateral edge of the front element and does not affect image quality.

[toups]

A caution regarding the disassembly video linked to in my previous post and the use of acetone.  The video stated the acetone ruined the finish on the exterior but they used acetone to help remove the rear section of the front lens assembly.  However if the interior parts are also of the same type of plastic, acetone could weld the threads together rather than loosening them.  Since I have not opened up the lens, I cannot comment further, but this is just a caution.

[Erik Lund]

The calibration of the rear elements of all of the fisheye lenses should be avoided, it's very difficult to recalibrate them.
I recall the huge challenge we had with Jacov's 16mm - Near impossible to get reliable focus back,,, Even though they have a huge depth of field!

[toups]

Thanks for the info.  Based on the warning on the service manual and your confirmation, I definitely will not remove the rear element group until there is no other option and the need is great which hopefully will never happen.

[toups]

Doesn't look like the front element group will easily unscrew, so I'll go with the can trick to protect the lens.  Will update when I get around to cutting the hood petals in a few days or so.  Thanks to Øivind Tøien for discovering that the tall thin cans are a fit to protect the lens.  Found some metal screw-in hoods on e-bay that may serve to make a screw in lens cap assembly.  Will detail when I update after cutting the hood petals.

[toups]

I assume that some of you may have found these sites but these were new to me. Definitely appropriate for this forum and thread, lots of technical details on this lens can be found at
https://web.archive.org/web/20161101215952/http://www.pierretoscani.com/echo_fisheyes_english.html
and
https://web.archive.org/web/20211028185202/http://michel.thoby.free.fr/Blur_Panorama/Nikkor10-5mm_or_Sigma8mm/Sigma_or_Nikkor/Comparison_Short_Version_Eng.html

The first link looks at the "shaved" version while the second is a reference for the first and dealt mainly with the unmodified lens.

[toups]

Mostly finished with the mod.

First the slightly bad news, I am not completely happy with where I trimmed the hood, however this is probably where it needs to be cut for the lens hood assembly that I decided to use.  If I were to do it all over again, I might do it a bit differently.  What I don't like is that the felt dust ring no longer seals against the body when the lens is at its closest focus position.

In order to maintain the seal at the closest focus point, the lens hood would need to be trimmed so that it extends about 7 or maybe 8 mm above the gold ring.  (However that is probably not far enough for the rings I added, see later discussion.)

I used a tall thin drink can to protect the lens and that worked perfectly!

I used a Dremel grinding wheel since the cut off wheels were not big enough to clear the drill press collet holder.  The grinding wheel is thicker than the cutoff wheels but worked well enough.  With the can I managed to not damage the lens housing.

I used a "58mm Meta Screw-in Hood with 62mm Cap for Olympus Pentax Leitz Panasonic Sony" https://www.ebay.com/itm/267053775696  (Note the misspelling of Metal)  Note this has a 62 mm thread end that I cut to make a 8.5 mm thick ring.  I used a product by Bircfhwood Casey called Aluminum Black Metal Finish to somewhat darken the cut edge.  Not as good as a true anodized and dyed surface but removes the gloss and blackens it somewhat.

I had to file the 62 mm inner surface slightly and ended up with a very tight press fit.  (In fact not sure I want to try to remove it again.  If it ever comes off I'll add a drop of glue.)

In order to cap the lens I use a "62mm Meta Screw-in Hood with 67mm Cap for Olympus Pentax Leitz Panasonic Sony" https://www.ebay.com/itm/267053775827  This hood is a bit longer than needed but was the closet I could find.  Right now I am using the plastic snap in cap but have ordered a "(2 Pcs) 67mm Metal Front Screw-in lens Cap Nikon Sony Pentax Minolta Lenses" [url]https://www.ebay.com/itm/225469187197[/ur/] that I might glue to the 2nd lens hood to make the screw off cap.  Actually I could probably make the original Nikon lens cap work with some effort and some shims.  Here is the lens with the hood/cap using the plastic cap that came with the hood.  Waiting for the metal cap to arrive.


Here is the lens uncapped.


Long story short, I am very happy with the way it turned out.  I'm just wondering if I should do something with respect to the dust seal.  Other than that I love it.  Thanks to all for the suggestions and details in this thread.  Will post an updated picture when the metal cap comes in.

[Erik Lund]

You definitely cut too much off. I’m afraid it’s not really possible to uncut 
Only fix is to glue on a ring to reseal it.