olemikey Loc: 6 mile creek, Spacecoast Florida

Hi jellis56, Read this post prior to attempting repair. 4th lens group looks easy, it is not.

I think I may be able to offer some quality info on this. I do have the Nikon Factory Repair Manual for 18-200 VR, and I do have at least one donor lens in 18-200 VR model, and it has an excellent rear element , on this lens it is called lens element group #4, or lens group #4.

I would be glad to sell it or parts to help you out: But - Caveat: Honesty is a virture, and I value mine: According to the manual, to disassemble/work on group #4, you need to know this first:

This is copied from the manual, not my interpretation;

※ Before Disassembly / (Re)assembly / Adjustment
On this lens, the VR (vibration-reduction) unit is mounted to correct the picture blur.
In order to maintain the functional accuracy of the picture blur correction, if detaching the VR
(vibration-reduction) unit and gyro base plate or if removing the main PCB unit, be sure to adjust the VR by
using the VR lens adjustment equipment (J15380）.
However, if disassembling the parts except the above, the VR adjustment is NOT necessary.
At service agencies where the "VR lens adjustment equipment" is not available/prepared, do NEITHER disassemble
NOR repair the products of the above case.

And, equally important, also from the manual:

Caution: 4th lens group (rear group):
When the 4th lens group is removed, it becomes necessary to perform lens alignment work after assembly. At service facilities where the alignment work is impossible, do
not remove the 4th lens group.

You also need some special fixtures/Jigs, computer aided laser alignment jig, and the appropriate lens repair tools.

If you have no experience with modern lenses, I recommend you look into a good shop, or it may be cheaper and easier to buy another used "working" 18-200, perhaps from a vendor like MPB.com, UsedPhotoPro, KEH, Camera dealers like B&H, Adorama, or Ebay, etc. one with "refund and warranty" would be good. Sell the one you have for parts.

So, and again, I hope this helps,

First, if you can't clean up the spot with microfiber and lens cleaner, or rubbing alcohol.....do some test shot as mentioned and make your best determination as to whether or not your photos are impacted. If you see no discernable impact to the photo, you could just live with it. If the eraser ruined the coating, ouch. I just tried a standard pencil eraser - Dixon Oriole #2 on and old Nikon front element, and it did no damage, did you use an ink eraser, or abrasive eraser, or rub it extremely hard? You could also try rubbing some high quality automotive wax on the element (not a cleaner wax, or wax with any abrasives) even candle wax, or silicon wax, a crayon, and polishing that carefully....you will know if it helped.

If you decide to repair, find a good shop, and need a donor lens...PM (private message) me, and I will sell my lens, or parts from it for a very reasonable price + shipping, I'm not a gouger. The actual repair is going to cost $$, so carefully consider your options.

I won't go any further on this now, but do hope this is helpful in your decision. Good luck.
PS - if you can find one reasonable, you might like the 18-300 even better, I do.

jellis56

Thank you, this is the info I was looking for. Going to chock up the scratch repair as a lesson learned and look for a 18-300 lens instead. Appreciate you taking the time to inform me...

olemikey Loc: 6 mile creek, Spacecoast Florida

Your welcome. I buy and repair old lenses, mostly for my own use. Have learned a lot about them over the last few years. I'll do a bit more research, but I don't think you can replace the external element in group 4 without major disassembly, and disturbing the focus stack. If I find that you can I'll PM as quick as I can, and let you know.

saxman71 Loc: Wenatchee, WA

A pencil eraser? Now that's thinking out of the box. Out of curiosity, did you take some shots with the lens before attempting to erase the scratch to see if the scratch was real problem? Sometimes little lens defects don't really show up in real world usage. Have you tried it since you finished your "repair work". Does the scratch/defect adversely affect your shots?

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Really, giving you the toll free number to Nikon was useless? So you still feel qualified to fix the lens after taking an eraser to a scratch on the rear element? You are useless, just like your supposed fix. Why don't go google "how do I get a new brain? ". That would be useful in YOUR case.

bwana Loc: Bergen, Alberta, Canada

I wouldn't have even bothered with the scratch. I've seen pix off a lens with the whole front element broken and didn't see any image degradation. Shoot some test shots. I'm sure they'll be just fine!

bwa

GoofyNewfie Loc: Kansas City

Like this?
https://www.lensrentals.com/blog/2008/10/front-element-scratches/
It’s pretty amazing, considering all the damage.

I’m not so sure about damages to a rear element would be as forgiving.
See this article: https://onfilmonly.com/damaged-lens-rear-element-scratch-test/

bwana Loc: Bergen, Alberta, Canada

'Rear Lens' article was a good read. So it all depends on where & how bad the damage, how you use the lens, the aperture, etc. Might or might not work under certain circumstances. May not be worth the cost of repairing...

bwa

GoofyNewfie Loc: Kansas City

Yes, one of those “depends’ situations.
It’s also interesting how little internal dust in a lens affects photos.
I just sold an older 80-200 2.8 with quite a bit of internal dust.
Did side by side test with my 70-200 2.8.
Couldn’t tell the difference between the two.
I suspect it would show up in the out of focus highlights as spots in the bokeh balls, but not certain.

mas24 Loc: Southern CA

I have seen professional photographers, have scratches and dings on the outside barrel of their lenses. They don't usually scratch the front nor rear glass of their lenses. They use Zeiss lens wipes after each shoot. And, I took their recommendation. And I am not a pro.

FTn

You didn't ruin this lens. It was ruined before you got it. The person who sold this lens to you should be shot by a firing squad and then charged for the bullets if they didn't disclose the damage to the rear element. Your attempts to repair the damage were creative but this is not a DIY project. The cost to replace the rear element and realign the elements and VR will probably be more than buying another lens. So chalk this up to a learning experience and start looking on the reliable vendor websites for another lens. You may also want to look at the reviews for the Nikon 18-200 and the 18-300 before you buy.

- FTn

amfoto1 Loc: San Jose, Calif. USA

Scratches or dirt on a rear lens element is the worst possible place to have it. While some specks of dust on the front element or inside a lens won't show up in images, any flaws on the rear element almost certainly will have an effect.

You may well have made matters worse with your amateur "repair" efforts using highly inappropriate "tools" like a pencil eraser!

Most likely the scratch will cause flare.

First clean the lens element as carefully as possible. Use proper lens cleaning solution (CD cleaner is probably okay) and either optical swabs or a fresh, clean micro fiber cloth. Be sure any dust is removed before doing any wiping with the swab or cloth, because some particles might be hard enough to damage the glass and the optical coatings on it.

Rubbing the lens with the eraser might have damaged those coatings. This may be the "haze" you're seeing. Try to clean it gently with a cloth or swab dampened with a few drops of cleaning fluid. Hopefully whatever the eraser left of the lens will come off.

Lens cleaning fluid can leave a very slight haze on optics. As a final cleaning step, best practice is to gently use a Lens Pen, to remove all traces of that haze and polish the surface to sparkling cleanliness that will be somewhat resistant to dust, etc. (DO NOT USE automotive polishes or waxes of any type on the optical surfaces. Any polishes will almost certainly ruin the coatings on the lens. You certainly don't want coatings of wax on them, either. That will almost certainly cause smears.)

Now you're ready for the "repair"...

Once the lens is sparkling clean, use a fine tip, permanent black marker or a very fine brush with India ink to lay down some ink, filling in the scratch. Carefully clean off any excess, only filling the scratch itself with ink. Unless it's really large, this will make the scratch "disappear" in images and prevent flare. There will still be some loss of resolution, but it will be slight.

A few times I've successfully "repaired" scratches in lenses using the black ink method described. I can only recall ever doing that with scratched front elements, but was able to continue shooting with the lens with little or no noticeable effect on images. (Actually it's pretty amazing how much damage a lens can have to front element or even internally and still make surprisingly good images... But NOT the rear element. Fortunately that's usually well protected inside the camera.)

Nikon doesn't sell replacement parts like the rear element (actually probably a group of elements). Except for a few mostly "cosmetic" external items (like rubber grips or replacement battery doors), they have a policy of NOT selling parts to the general public. In fact, they've recently further tightened this policy and will no longer provide repair parts even to their own 15 or 20 "authorized repairers". So your only choice to have a new element installed would be to send the lens to Nikon factory service center and have them repair it. If it was a "gray market" purchase originally, they may refuse to do any repairs on it (they can tell by the serial number).

You might be able to find an independent repair shop that has another 18-200mm "donor" lens, with other damage but usable parts needed by your lens. Email some of them and ask. Many of them are now in the habit of squirreling away broken Nikon gear they acquire various ways, since the company policy makes getting new replacement parts next to impossible. They will likely only be willing to sell the part if they also make the repair though.... But would probably be less costly than Nikon's own repair facilities. Plus, independent repairers might work on gray market items that Nikon refuses to touch.

I've bought stuff off Craigslist. The problem is that it's usually a private party sale and purchase, so there's no warranty or any right of return, if there's something wrong with the item. But one of the advantages of CL is that most purchases are done in person, so you can carefully inspect the product before handing over your money. When I purchase a used lens, I take a small flashlight to inspect the optics inside and out. There's always some dust and may be some minor wear and tear on the barrel, but I want the optics to be as good as possible. Typically I'd reject any lens with fungus inside, uneven aperture leaves, focus or zoom rings that don't operate smoothly, obvious damage or heavy wear & tear, peeling lens coatings or separating elements... or a scratch on the rear element.

I was excited to find a really good deal on a Leitz lens at a second hand store... until I looked inside and saw coatings flaking off some of the internal surfaces. I didn't buy it.

But I did buy a vintage Canon FDn 50mm f/1.4 lens with a damaged rear element very cheap at a flea market. It's otherwise unusually nice... looks virtually unused in all other ways... so I was planning to replace the rear element myself. But have not been able to do so for lack of parts. Maybe some day I'll find a donor lens!

I also made an exception and bought another vintage lens knowing in advance it had internal fungus... Only because it's an extremely rare 800mm that I was able to buy for less than 1/4 the usual value... and because I knew that it's very simple optically (one group of two elements) and easy to disassemble for cleaning. I don't plan to use it for serious shooting anyway, it will primarily be a display piece.

Vintage lenses without electronics are usually pretty easily repaired... On many, it's just a matter of removing the mount mechanism and then the rear element group simply unscrews.

But that's not the case with many modern lenses with electronic controls for autofocus, image stabilization and aperture control. They can be really difficult to disassemble. Especially the lenses with a lot of plastic components. More "entry level" models may even snap together and/or be assembled with glue.

jellis56

thank you for sharing all of that information. I've been taking more test shots trying to see if my DIY repair caused more damage than what was originally there with the scratch.

Can someone tell me the best way to take shots to see?

Should I take some shots in daylight against a white background or colors?etc... Let me know what to take pics of and I'll figure out how to post online. I've diminished about half the scratch with my efforts and the haze spot has decreased, now I'm just seeing a little discoloration when I hold the lens under the light just right.


Thanks

Insp Gadget Loc: St Louis area

Why do you feel you have to be an ass to someone who made a mistake and is asking for help. I f you're not going to help, just shut up and keep your anger to yourself.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

I gave him the number to Nikon, toll free number, and info on who to ask for. What advice did you offer? I have no anger, nothing but help to offer, unlike many others on this site.