Author Topic: AF Nikkor 20mm f2.8 damaged front.  (Read 2914 times)

richardHaw

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #15 on: March 01, 2018, 09:30:50 »
temperature will probably have a bigger impact  :o :o :o

modern lenses shouldn't matter except for probably the 55/2.8 or lenses that are known to be troublesome with oil on iris.

it is true for lenses that were lubricated the old way using whale oil or other less stable old style grease. i am cleaning older and older lenses these days (pre-war Zeiss) and you can see the pattern on how the grease migrated just by looking at the mold marks where the fungi has left marks after eating the oil.

storing a lens with the aperture wide-open or close will also have an impact. i thought that this was an old wives' tale until I began working on the first Nikkors and older RF lenses. for automatic aperture lenses, the spring will weaken when left tense for a very long time, I had to replace springs a few times because of this. for RF lenses, the iris may be stuck with corrosion from the oil when stored wide-open. i know this sounds silly but I can now say that there is some truth to this.  ::) unfortunately, some people will forget about a lens and the next time the lens is exercised will be a couple of decades later...by a grandson or stranger.  :'(

Seapy

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #16 on: March 01, 2018, 09:53:34 »
Thank you both, the trouble with things like this is that as Richard says, it is a long term thing.  The open - closed iris had not occurred to me, I can see the reason it could matter, springs can take a 'set' if left expanded or compressed for long periods, age hardening may also play a role.  Are you saying better open, or better closed?
Robert C. P.
South Cumbria, UK

Erik Lund

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #17 on: March 01, 2018, 10:51:22 »

,,,,,,,storing a lens with the aperture wide-open or close will also have an impact. i thought that this was an old wives' tale until I began working on the first Nikkors and older RF lenses. for automatic aperture lenses, the spring will weaken when left tense for a very long time, ,,,,,




Yes it does loose tension over time from not being used, however it also loses tension from use, it's called creep.


So saying it is one or the other from storage open or closed,,, difficult/impossible call IMHO,,,
Erik Lund

richardHaw

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #18 on: March 01, 2018, 11:08:11 »
Thank you both, the trouble with things like this is that as Richard says, it is a long term thing.  The open - closed iris had not occurred to me, I can see the reason it could matter, springs can take a 'set' if left expanded or compressed for long periods, age hardening may also play a role.  Are you saying better open, or better closed?

depends, really. so long as the spring isn't tense. :o :o :o
the "old wive's tale" that i have been hearing since the 80s was to store the lens with the iris left at mid-range of the opening, maybe about f/5.6. i shrugged it off as BS before.

I am currently servicing an early Contax 2a from 1951(?) and a few weeks ago, a couple of Nikon S's and some springs on the Nikon S's had to be re-tensed to make them thing work. I was referring to the high speed pawl and the long spring underneath. on the Contax, the spring for the slow governor has lost its tension so its a stop faster than ideal. these cameras were probably stored for decades like this and this is the result.

i grew up in a watch repair shop where I was an apprentice and we would sometimes get watches older than some countries in Europe, Asia or Africa and some of the springs just lost their tension so the escapement won't work anymore. I guess it is inevitable. nothing lives forever trouble-free, including machines.

of course, constant use like what Erik mentioned can also contribute to this. our neighbor next door is a camera shop and they did spring changes or re-tensing on the then-current-model FMs, etc on a constant basis (from pros i assume).

I asked somebody at Nikon and he advised that storing a lens with the bayonet facing down is generally thought of as the best because it is structurally the strongest part of the lens. this has nothing to do with oil but probably more to do with the delicate gearing of current AF lenses specially if they are heavy. ::)

Erik Lund

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #19 on: March 01, 2018, 11:32:42 »
Yes I agree :)
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richardHaw

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #20 on: March 01, 2018, 11:43:37 »
i asked him this because there was a very long discussion on a forum that I was active in long ago about storing lenses. the biggest no-no according to him is storing new AF lenses on its side specially the ones with VR as they can be misaligned. he also told me that the VR element is so sensitive that it can get misaligned just through constant use and will have to be sent to Nikon to re-calibrate on a regular basis.  :o :o :o maybe this is true if you are a pro. i went to the Nikon warehouse for repairs and true enough, the lenses are not stored sideways but up or down. the ones on the workbench are a different story, maybe because they will not be stored like that for a long time ::) i got into the storage room because i wanted to try their 50/1.2 but thats a different story.

Seapy

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #21 on: March 05, 2018, 18:10:52 »
The lens front is now finished apart from the cap and final coating.

Cutting the petals was tricky, I made a little template for the cut outs but in the end I had to do it by measurement.  I couldn't get rid of the vignetting at the corners.  I needed to make the cutouts symmetrical by measurement.  That worked by hand filing and repeatedly test fitting.







The lens shade looks a little scrappy in these pictures but it's mostly reflections, rubbed down and painted I am sure it will be quite nice.  My 16mm fisheye is quite battered and scraped around the front end so it should match!.

What would anybody recommend to paint the lens hood with?  I was intending to get it anodised but I wonder if a matt black spray paint might be better?

I am intending to make a push on (clip on?) cap similar to  the 16mm Fisheye cap.
Robert C. P.
South Cumbria, UK

Matthew Currie

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #22 on: March 05, 2018, 19:22:41 »
Matte black paint doesn't wear terribly well, but on the plus side it's dead easy to freshen up.  I've used brush-on semi-gloss Rustoleum to clean up the edges of AI-milled lenses and the like, and it works pretty well there.  I would guess that a similar thing in spray would be pretty effective here as long as you don't worry about the edges wearing off almost immediately.  If you wanted to get fancy you could even do the outside with more gloss than the inside.

Seapy

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #23 on: March 05, 2018, 19:36:56 »
Thanks Matthew,  I think I have some black Rustolium in aerosol.  I use Rustolium quite a bit, I have some primer which is specially for aluminium.  I will try it!

I forgot to mention above that I have ribbed the inside of the hood to help reduce the internal reflections, hopefully.
Robert C. P.
South Cumbria, UK

Erik Lund

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #24 on: March 05, 2018, 20:14:52 »
Humbrol Enamel is quite strong, and not IR reflective  ;)

33 is Matt Black
Erik Lund

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #25 on: March 06, 2018, 02:20:37 »
I have also had good results with Humbrol 33 (Matt Black) on top of aluminium etch primer (I got some such primer from a panel beater/motor car painter).  Rub the primer down really lightly with very fine grit paper - around 800.

An alternative is blackboard paint for larger areas, but I do like the matt Humbrol - it is good for hiding witness marks in the metal.
Hugh Gunn

Akira

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #26 on: March 06, 2018, 02:39:24 »
I'd like to see it finished in black anodize with the internal part painted in mat black using either of the suggested paint.  :)
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richardHaw

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #27 on: March 06, 2018, 02:59:29 »
Humbrol's matte black is better than Tamiya's. Testrol's not so bad too  :o :o :o

Seapy

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #28 on: March 06, 2018, 10:05:58 »
Akira's option seems to me the best way, I am planning to anodise my pano head but cost is a factor which is getting in the way right now.

I will look at anodising kits first but rather lack confidence to get involved in chemistry.  Don't want to ruin the appearance of my work by spoiling it with a shoddy anodising job.

You can get aerosol etching primer, Rustoleum themselves do an aluminium primer but it's brush on, sort of rubbery?  It balls up if you don't leave it with a single stroke of the brush, almost like rubber glue or Evostick, can make a right mess, being rubbery it doesn't rub down either. 5 for a tiny tin, the last one I had got knocked over by accident...  >:(

I have a Humbrol agent in town, will have a chat with them.  I can always strip the paint and get it anodised in the future when funds improve.  For now I just want it black so I can use it.

I have looked at flocking the inside of the shade and the inside of the cap,  apparently a very simple process but not sure it's a good way forward durability being one concern.  I think the inside of my 16mm fisheye lens cap is coated with flocking, it grips nicely but before making it I would need to know exactly how effectively thick the coating would be, applied manually it may vary. The cap might not go on if it's too tight or might be loose/fall off if too slack, the difference will probably be small between one and the other.

I have looked at the 16mm fisheye cap, it consists of three parts, a tube, a threaded retaining ring and a thin disk, 1.4mm, with the "Nikon" lettering which is retained in the tube by the threaded ring.

I don't really want the complications of making mine in three pieces, screw cutting such fine threads in such delicate pats seems a wast of effort for little gain, however, I will find it very hard to make the disk part as thin as the Nikon one because it may not machine easily, it will tend to bend away from the lathe tool, even with very light cuts, so I am limited how thin I can go by making it in one piece.
Robert C. P.
South Cumbria, UK

richardHaw

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Re: AF Nikkor 20mm f2.8 damaged front.
« Reply #29 on: March 06, 2018, 10:52:20 »
anodization doesnt really cost much  :o :o :o
you just have to contact the correct people  ::)

my friend made tattoo machines and he had his done by a bike parts maker. basically when the bike shop is going to anodize something they will just include his parts with theirs.