Nikkor AF 20mm f/2.8D, blurry lens element !

[DomFR]

Hello all,

I bought a Nikkor 20mm f/2.8D a few months ago and I badly discovered that it has an optical defect: blurry lens element which might have been damaged by an unnapropriate direct exposure to the sun... wicked seller!

I am looking to change the defective part (a block of two lenses sealed together inside a metallic rign). I already contacted Nikon spare U.K. who provided the wrong part number (1B100-498-2 = rear lens element) and, as a consequence, delivered me the wrong part a few days ago!! :-(

Could anybody help me to identify the part number (need access to Nikon SAV schematics) ?

Does anyone sell a defective Nikkor 20mm f/2.8 that I might use to repair mine ?

Thanks for your help !

Dominique


Lens schematic (without part number ...), damaged part is painted in green


Picture of the damaged part (it seems ok but the coating, probably the glue, is blurry and affect image quality)

 

[fradn91]

Hello all,

I bought a Nikkor 20mm f/2.8D a few months ago and I badly discovered that it has an optical defect: blurry lens element which might have been damaged by an unnapropriate direct exposure to the sun... wicked seller!

I am looking to change the defective part (a block of two lenses sealed together inside a metallic rign). I already contacted Nikon spare U.K. who provided the wrong part number (1B100-498-2 = rear lens element) and, as a consequence, delivered me the wrong part a few days ago!! :-(

Could anybody help me to identify the part number (need access to Nikon SAV schematics) ?

Does anyone sell a defective Nikkor 20mm f/2.8 that I might use to repair mine ?

Thanks for your help !

Dominique


Lens schematic (without part number ...), damaged part is painted in green


Picture of the damaged part (it seems ok but the coating, probably the glue, is blurry and affect image quality)

Hi!

I'm experiencing the exact same problem as you. How has it ended up eventually? I am longing to know if there's a cheap, DIY way to resolve this awful defect.

Thank you

 

[DAVID MANZE]

Hello all,

I bought a Nikkor 20mm f/2.8D a few months ago and I badly discovered that it has an optical defect: blurry lens element which might have been damaged by an unnapropriate direct exposure to the sun... wicked seller!

I am looking to change the defective part (a block of two lenses sealed together inside a metallic rign). I already contacted Nikon spare U.K. who provided the wrong part number (1B100-498-2 = rear lens element) and, as a consequence, delivered me the wrong part a few days ago!! :-(

Could anybody help me to identify the part number (need access to Nikon SAV schematics) ?

Does anyone sell a defective Nikkor 20mm f/2.8 that I might use to repair mine ?

Thanks for your help !

Dominique


Lens schematic (without part number ...), damaged part is painted in green


Picture of the damaged part (it seems ok but the coating, probably the glue, is blurry and affect image quality)

I had exactly the same thing with that lens, within the same rear couplet as yours! The glue had become misty giving a low contrast unusable result. I tried to de-cement the couplet with various volatile thinners, resorting even to boiling, but these two part glues resist them all....I tried looking on ebay for spares but I found nothing!

I didn't contact Nikon as I thought the price would make the lens non viable.

As it was purchased cheaply I decided to resell on ebay stating exactly the problem and listing it for spares or repairs. It sold quickly for £75 to a private repair company.

These older D series lens are beginning to show their signs of age in terms of glue mistiness , I tested a AF35-70 F2.8D and there was some de-laminating of the elements with that!

Both of these lenses should be examined very carefully before buying S/H with a bright torch to check for hazing and fungus........if you see a bit of fungus it still could be a usable lens......if you see hazing........walk away!

--

--
Dave's clichés

 

[StephenWong9W2XR]

I have the same lens n same problem, do u able to have the parts number?

Do u able to share with me n where can I buy this part.

Thanks

Stephen Wong

 

[glovisol]

PART I - General

I am replying because I wish to convey repair information on the Nikon AF 20 mm F/2.8.

The blurry retrofocus group is a common problem with old 20 mm lenses of this type. But this lens group can be cleaned and/or re-glued. To gain access, the back portion of the lens must be disassembled as follows:

1) first remove the 2 silver micro-screws holding the black contact.

2) Remove the 3 black micro-screws holding the black plastic inner ring.

3) Remove the 3 screws (2 silver, one black) holding the bayonet. Note the position of the black screw.

4) Lift off the bayonet and the spacer ring underside.

5) The rear lens group assy. ( as shown in the first post of this thread, is now in sight.

6) Using a lens spanner inserted in the two base slots, unscrew the group.

7) Note that the group, on the part opposite to the thread, has a black coated ring. Using a micro parrot spanner or a watchmaker vise, hold this ring and unscrew the lens assy holder using the lens spanner in the two slots again. BE CAREFUL, AS THE CENTER LENS MAY FALL OFF.

8) So you will now have three lenses apparently: the thick front one glued to the lens assy holder, one thin center lens and the back lens glued to its threaded holder. I wrote apparently, because the the thick front lens is made with two lenses glued together and normally it is this one which gives trouble.

9) All lenses may be dirty with evaporated glue and must be cleaned with Acetone. Lighter fluid or Optical Wonder are not effective with the evaporated glue covering the surfaces. The thick front lens can be removed from the assy by leaving it soaked in Acetone for 1or 2 hours. It is more easily cleaned if free.

10) Once cleaned, examine the lenses with grazing light to check the blur is gone, then re-assemble and or re-glue.

11) If anyone is still interested , I can post pictures of entire process.

How to put back together in PART II.

--
glovisol

 

[DAVID MANZE]

PART I - General

I am replying because I wish to convey repair information on the Nikon AF 20 mm F/2.8.

The blurry retrofocus group is a common problem with old 20 mm lenses of this type. But this lens group can be cleaned and/or re-glued. To gain access, the back portion of the lens must be disassembled as follows:

1) first remove the 2 silver micro-screws holding the black contact.

2) Remove the 3 black micro-screws holding the black plastic inner ring.

3) Remove the 3 screws (2 silver, one black) holding the bayonet. Note the position of the black screw.

4) Lift off the bayonet and the spacer ring underside.

5) The rear lens group assy. ( as shown in the first post of this thread, is now in sight.

6) Using a lens spanner inserted in the two base slots, unscrew the group.

7) Note that the group, on the part opposite to the thread, has a black coated ring. Using a micro parrot spanner or a watchmaker vise, hold this ring and unscrew the lens assy holder using the lens spanner in the two slots again. BE CAREFUL, AS THE CENTER LENS MAY FALL OFF.

8) So you will now have three lenses apparently: the thick front one glued to the lens assy holder, one thin center lens and the back lens glued to its threaded holder. I wrote apparently, because the the thick front lens is made with two lenses glued together and normally it is this one which gives trouble.

9) All lenses may be dirty with evaporated glue and must be cleaned with Acetone. Lighter fluid or Optical Wonder are not effective with the evaporated glue covering the surfaces. The thick front lens can be removed from the assy by leaving it soaked in Acetone for 1or 2 hours. It is more easily cleaned if free.

10) Once cleaned, examine the lenses with grazing light to check the blur is gone, then re-assemble and or re-glue.

11) If anyone is still interested , I can post pictures of entire process.

How to put back together in PART II.

It must be a question of lens cement is used in the actual lens ......... I tried acetone ...xylene ..... touline ........ the two latter dissolve most adhesives ......... then heating the couplet in the solvents etc .... and left them submerged for weeks ....... nothing touched the two component lens cement ...... they remained misty.

Older lenses used a balsam lens cement which can be dissolved fairly easily ...... I spent many hours surfing obscure lens repair sites ........ the situation was clear .. balsam cement dissolves ......... two part modern lens cements don't!!

--
Dave's clichés

 

[kkolehma]

I just bought used lens with this exact problem. Lens elements now sitting in acetone. In an off chance that cement dissolves, lenses probably should be re-reglued. Any suggestions on what glue to use?
Also if some one knows the part number or source for new lens element, that would be great...

--- Kari Kolehmainen

 

[davethebirder]

I just bought used lens with this exact problem. Lens elements now sitting in acetone. In an off chance that cement dissolves, lenses probably should be re-reglued. Any suggestions on what glue to use?
Also if some one knows the part number or source for new lens element, that would be great...

I can assure you that you will "never dissolve" that two part lens cement !! ........ I spent time and effort trying with stronger solvents than acetone ......

......... your only hope is to find another cheap/broken example where the rear couplet is still clear

davethebirder

 

[kkolehma]

I can assure you that you will "never dissolve" that two part lens cement !! ........ I spent time and effort trying with stronger solvents than acetone ......

......... your only hope is to find another cheap/broken example where the rear couplet is still clear

davethebirder

It certainly seems that way. My lens serial is 37xxxx (I don't have it in front of me) so it is from later half of 1994-2005 range. So not that old since I have Nikon lenses from 1980's that are perfectly clear still. Have to try to heat threat it over the weekend. Nikon does not sell just the rear lens group but whole inner body of the lens which comes with all lenses except for front one. It is 180 euros which almost doubles the lens price, but then it is a practically new lens. I will keep hunting for just rear element and trying to get those lenses apart.

 

[kkolehma]

I can assure you that you will "never dissolve" that two part lens cement !! ........ I spent time and effort trying with stronger solvents than acetone ......

......... your only hope is to find another cheap/broken example where the rear couplet is still clear

davethebirder

Let’s see. I got some progress after baking the lens in oven at 180 degrees. I got glue soft enough to separate lenses but still have the battle to get glue off from the convex lens surface. I am hopeful that it will soften enough to get it off.

Then it is a question whether it will produce decent images after getting everything together… far from certain…

 

[davethebirder]

I can assure you that you will "never dissolve" that two part lens cement !! ........ I spent time and effort trying with stronger solvents than acetone ......

......... your only hope is to find another cheap/broken example where the rear couplet is still clear

davethebirder

Let’s see. I got some progress after baking the lens in oven at 180 degrees. I got glue soft enough to separate lenses but still have the battle to get glue off from the convex lens surface. I am hopeful that it will soften enough to get it off.

Then it is a question whether it will produce decent images after getting everything together… far from certain…

I must admit I fell short of baking the couplet in the oven ........ but I did boil it in various volatile solvents ........ good luck with i though !!

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davethebirder

 

[kkolehma]

I can assure you that you will "never dissolve" that two part lens cement !! ........ I spent time and effort trying with stronger solvents than acetone ......

......... your only hope is to find another cheap/broken example where the rear couplet is still clear

davethebirder

It seems the glue is no match for espresso machine cleaning solution. The stuff that dissolves coffee stain buildup. I managed to get the glue off from lens surface by placing the lens into glass jar with strong solution of the coffee machine cleaner and placing the container in ultrasonic cleaner for about 60 minutes at 70°C temp. After that it was possible to get glue residue away from lens by rubbing with micro fabric.

Result is much improved pictures even now without replacing the glue. I ordered optical glue from GO Edmunds with refractive index of 1.52 which should be close to Canada balsam and hopefully close to what ever glue was used in the lens originally.

I start to get cautiously optimistic that lens may turn out to be OK after all since it was focusing also OK. Still not nowhere close to as clear as Sigma 24 EX DG.

 

[davethebirder]

I can assure you that you will "never dissolve" that two part lens cement !! ........ I spent time and effort trying with stronger solvents than acetone ......

......... your only hope is to find another cheap/broken example where the rear couplet is still clear

davethebirder

It seems the glue is no match for espresso machine cleaning solution. The stuff that dissolves coffee stain buildup. I managed to get the glue off from lens surface by placing the lens into glass jar with strong solution of the coffee machine cleaner and placing the container in ultrasonic cleaner for about 60 minutes at 70°C temp. After that it was possible to get glue residue away from lens by rubbing with micro fabric.
Result is much improved pictures even now without replacing the glue. I ordered optical glue from GO Edmunds with refractive index of 1.52 which should be close to Canada balsam and hopefully close to what ever glue was used in the lens originally.
I start to get cautiously optimistic that lens may turn out to be OK after all since it was focusing also OK. Still not nowhere close to as clear as Sigma 24 EX DG.

I tip my hat to you there ...........

So, oven bake to separate the elements ...... ultrasonic cleaner ....... and a light rub with a micro fabric cloth ....... plus finding the appropriate lens cement ....... excellent !

...... I will say that I think the lens used a two part modern lens adhesive as balsam cement separates fairly easily which is when you find separation around the edges so the new cement could turn out to have the right refractive index.

I spent some time reading about difficulties and failures trying to separate couplets and was still determined ..... tried fairly hard but fell at the sixth hurdle ...... where you came across the line. ....

Bravo and excellent work ! ....... it will be interesting to know the end result.

https://www.flickr.com/photos/124690178@N08/

davethebirder

 

[kkolehma]

In the end the result wasn't so good. Getting the lens to focus accurately especially wide open is difficult. Tolerances are just so small that it does not seem to be feasible. Haze I got rid of, but result is still inferior to my Sigma 24mm f1/8 EX DG lens with such a big margin that I doubt I will mount this lens ever...

 

[davethebirder]

In the end the result wasn't so good. Getting the lens to focus accurately especially wide open is difficult. Tolerances are just so small that it does not seem to be feasible. Haze I got rid of, but result is still inferior to my Sigma 24mm f1/8 EX DG lens with such a big margin that I doubt I will mount this lens ever...

I'm sorry to hear that your 20mm F2.8D did not respond to treatment ...... you got so far with it !

I wonder if the ultra-sonic cleaner didn't de-polish the surfaces a little ....... something is causing that flare .......

Like mine it will sell on ebay to someone who's looking for spare parts other than the rear group ......... just list the problem ........

Brave effort nonetheless !!

https://www.flickr.com/photos/124690178@N08/

davethebirder

 

[Camillo]

Hello all,

I bought a Nikkor 20mm f/2.8D a few months ago and I badly discovered that it has an optical defect: blurry lens element which might have been damaged by an unnapropriate direct exposure to the sun... wicked seller!

I am looking to change the defective part (a block of two lenses sealed together inside a metallic rign). I already contacted Nikon spare U.K. who provided the wrong part number (1B100-498-2 = rear lens element) and, as a consequence, delivered me the wrong part a few days ago!! :-(

Could anybody help me to identify the part number (need access to Nikon SAV schematics) ?

Does anyone sell a defective Nikkor 20mm f/2.8 that I might use to repair mine ?

Thanks for your help !

Dominique


Lens schematic (without part number ...), damaged part is painted in green


Picture of the damaged part (it seems ok but the coating, probably the glue, is blurry and affect image quality)

Man I was thinking of getting this lens for use with my gymbal cause of the price and lightweight but it appears to be a problematic lens then.... Should I stay away? is there an alternative?

thanks for posting!

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[RC1962]

A bit late to the thread, but:

"I wonder if the ultra-sonic cleaner didn't de-polish the surfaces a little ....... something is causing that flare ......."

Yes. Without doubt. Ultrasonic cleaners will micro-etch many types of glass.

As for separating cemented doublets (pairs of cemented lenses are doublets, not couplets) that have been cemented with modern cements, pretty much only methylene chloride is the only solvent that will do the job. Even then, look at the potential of two to four weeks soaking. And that chemical isn't something pleasant, isn't easily available and requires a government issued permit to buy in the UK.

For re-cementing, accuracy of centring is critical to get the very best results, and the correct cement to use is Norland NOA61 which is a rapid UV cure type, but you do get a bit of time to adjust positioning with a short pre-cure UV flash, before hitting it with a second blast of UV to set it off. Also it has a very short shelf life of a few months and must be stored in the dark.

Having said all of that, it is entirely feasible to re-cement lens pairs at home with a modicum of equipment and common sense and end up with very good results.

 

[Mole Delta]

In the interest of balance, mine works wonderfully.

 

[davethebirder]

A bit late to the thread, but:

"I wonder if the ultra-sonic cleaner didn't de-polish the surfaces a little ....... something is causing that flare ......."

Yes. Without doubt. Ultrasonic cleaners will micro-etch many types of glass.

As for separating cemented doublets (pairs of cemented lenses are doublets, not couplets) that have been cemented with modern cements, pretty much only methylene chloride is the only solvent that will do the job. Even then, look at the potential of two to four weeks soaking. And that chemical isn't something pleasant, isn't easily available and requires a government issued permit to buy in the UK.

For re-cementing, accuracy of centering is critical to get the very best results, and the correct cement to use is Norland NOA61 which is a rapid UV cure type, but you do get a bit of time to adjust positioning with a short pre-cure UV flash, before hitting it with a second blast of UV to set it off. Also it has a very short shelf life of a few months and must be stored in the dark.

Having said all of that, it is entirely feasible to re-cement lens pairs at home with a modicum of equipment and common sense and end up with very good results.

Thanks for your response ........ however, given the restrictions of obtaining this methylene chloride and nasty as that sounds with it's long soak time and possible alignment issues, one wonders if it's the worth money/time/ effort .....

....... and as this lens has a little bit of a reputation for misting the rear couplet, I would avoid buying one (as mine had the same issue)....... many of the wide angle AF-D series have no couplets and as such have no risk of that happening ... for those who have lens cement concerns see below:

AF24mm F2.8D ..... 9 elements in nine groups ........ no couplets

AF28mm F2.8D ..... 6 elements in six groups .......... no couplets

AF35mm F2D ..... 6 elements in 5 groups ......... one couplet

AF50mm F1.8D . 6 elements in 5 groups .......... one couplet

AF60mm F2.8D ...... 8 elements in 7 groups ........ one couplet

AF85mm F1.8D ........ 6 elements in six groups ....... no couplet

AF85mm F1.4 ........ 9 elements in 8 groups ........ one couplet

AF105mmm F2.8D ..... 9 elements in 8 groups ........ one couplet

and so on ........ here's Ken Rockwells site with all the D lens specs!

https://www.kenrockwell.com/nikon/nikkor.htm#af

....... thanks ......

https://www.flickr.com/photos/124690178@N08/