NikonGear'23

Gear Talk => Lens Talk => Topic started by: ArthurDent on May 13, 2018, 00:41:19

Title: How to remove the coating from a lens?
Post by: ArthurDent on May 13, 2018, 00:41:19
I have a candidate lens for uv and want to remove any coatings which might reduce uv transmission. Any suggestions as to abrasives I should use? How to apply them? How to keep the abraisive out of the lens? Other important considerations? Thanks for any suggestions.
Title: Re: How to remove the coating from a lens?
Post by: Birna Rørslett on May 13, 2018, 01:13:36
Use the lens for UV first. Removing coating(s) might damage the optical performance so always best to test beforehand. Don't expect superior UV response from most lenses, whether they have coating intact or not.  However, the target one aims for will dictate whether more humble optics can serve nonetheless.
Title: Re: How to remove the coating from a lens?
Post by: ArthurDent on May 13, 2018, 02:50:25
Thank you, I will certainly try that first.
Title: Re: How to remove the coating from a lens?
Post by: Seapy on May 13, 2018, 05:59:38
Having been there and done it...  I had a 100mm E lens, a very nice example, near new.  I understood it was a reasonable candidate, so I set to with Dremel and some car polish, the coating was very tough to remove and the lens lost it's sharpness, a lot of work to ruin the lens!

Apart from UV transmission, the biggest issue with UV is focus shift.  Depending on the lens, focus shift can be very significant.  You focus on the subject, then fit the UV pass filter, make the exposure.  The results will likely be oof.  If you lay a tape measure or ruler on  a desk, focus on say the 100mm mark, then photograph it from above at 45º, observe where the best sharpness occurs.  Refocus so that the 100mm mark is sharpest and observe the difference.  I used a rail, from memory at about 350mm subject to lens, with ~ 100mm lens, I found the offset was about 14mm but it varies lens to lens.

Initially I used a Metz 45CT with (most but NOT ALL) the yellow coating removed from the tube.  Later I constructed a Nichia 365nm UV lamp with a special focusing fluoride? lens, which works well. Less savage than the Metz.

(https://farm1.staticflickr.com/980/40263607020_26ebb0e950_o.jpg)

(https://farm1.staticflickr.com/827/28198408618_447c4c5031_o.jpg)

I tried various lenses but the Micro Nikkor to me seemed as good as any I have, although I do now have an EL 105mm f/5.6 lens with a helicoid. I have yet to try that combination.

A couple of images taken with this setup, Rudbeckia in UV: D200UV with Micro Nikkor 55mm f/2.8.

(https://farm1.staticflickr.com/970/42071124741_41614ee7bc_o.jpg)

Dandelion in UV.

(https://farm1.staticflickr.com/830/42071123891_ef605ca08a_o.jpg)

Not forgetting IR, Rudbeckia, with my 720nm D200 and I think the Micro Nikkor 55mm f/2.8.

(https://farm1.staticflickr.com/943/42071415761_36153efe1e_o.jpg)

Last but not least, I rather like the induced fluorescence effect, gerbera daisy, visible spectrum D200 camera, illuminated with my Nichia 365nm lamp and I probably used the Micro Nikkor 55mm f/2.8.

(https://farm1.staticflickr.com/957/42071416261_473b1e2a69_o.jpg)

Hope the above is some help, do NOT claim expertise, a lot of fumbling in the dark (literally!).  Much assistance from Klaus with the  filters and lighting and from Bjørn's website etc. to surmount the obstacles.

Title: Re: How to remove the coating from a lens?
Post by: Øivind Tøien on May 13, 2018, 09:06:10
The UVIVF of the daisy is excellent, very nice colors!

Do you recall what kind of WB/color correction that was used?
(We have a current discussion about possible needs to warm up UVIVF captures on the UV forum site).
Title: Re: How to remove the coating from a lens?
Post by: Seapy on May 13, 2018, 10:02:37
The UVIVF of the daisy is excellent, very nice colors!

Do you recall what kind of WB/color correction that was used?
(We have a current discussion about possible needs to warm up UVIVF captures on the UV forum site).

Thank you Øivind, I rather like them too, one of my favourite compositions!  They were processed in Lightroom so yes I have all the detail.

Rather than incur the wroth of the Northern Bears,  ;D  I will start another thread in the Processing section, I don't want to spend three weeks in the wilderness!  ::) LOL

I am also a member of the UV group but it's so long since I partook I have probably lost the url and my password...
Title: Re: How to remove the coating from a lens?
Post by: Øivind Tøien on May 13, 2018, 10:36:41

I do not think the Northern Bear would mind, do whatever you find most suitable.

The UV forum site URL: http://www.ultravioletphotography.com (http://www.ultravioletphotography.com)
Title: Re: How to remove the coating from a lens?
Post by: Birna Rørslett on May 13, 2018, 10:53:42
Seapy: I can reset your password on UVP if you wish. Send me a PM and get the username and a temporary password in return.
Title: Re: How to remove the coating from a lens?
Post by: richardHaw on May 13, 2018, 12:07:53
ammonia and other chemicals will do that for you. easier for early Zeiss T coating since water is all it takes  :o :o :o
Title: Re: How to remove the coating from a lens?
Post by: Seapy on May 13, 2018, 13:28:35
Seapy: I can reset your password on UVP if you wish. Send me a PM and get the username and a temporary password in return.

Thank you Birna, I will check my little red book, I may still have them.  If so I will log in again.
Title: Re: How to remove the coating from a lens?
Post by: ArthurDent on May 13, 2018, 19:58:21
ammonia and other chemicals will do that for you. easier for early Zeiss T coating since water is all it takes  :o :o :o

Richard, Do you think ammonia would work on the Nikon 50mm f/1.8 ais? My plan would be to suspend it with the front of the lens pointed down and to use a q tip saturated with ammonia to remove the coating, then use kimwipes to remove any excess, unless there is a better way?
Title: Re: How to remove the coating from a lens?
Post by: Dr Klaus Schmitt on May 13, 2018, 20:04:04
I have a candidate lens for uv and want to remove any coatings which might reduce uv transmission. Any suggestions as to abrasives I should use? How to apply them? How to keep the abraisive out of the lens? Other important considerations? Thanks for any suggestions.

This is an urban myth basically, old and honestly forget about that. There are so many good candidates for UV photography which do not require any such ...

Have a look here on my Blog and you'll find plenty: http://photographyoftheinvisibleworld.blogspot.com/2011/01/uv-lenses-tested-good-for-uv.html (http://photographyoftheinvisibleworld.blogspot.com/2011/01/uv-lenses-tested-good-for-uv.html)
Title: Re: How to remove the coating from a lens?
Post by: Akira on May 13, 2018, 20:17:27
Apart from UV transmission, the biggest issue with UV is focus shift.  Depending on the lens, focus shift can be very significant.  You focus on the subject, then fit the UV pass filter, make the exposure.  The results will likely be oof.  If you lay a tape measure or ruler on  a desk, focus on say the 100mm mark, then photograph it from above at 45º, observe where the best sharpness occurs.  Refocus so that the 100mm mark is sharpest and observe the difference.  I used a rail, from memory at about 350mm subject to lens, with ~ 100mm lens, I found the offset was about 14mm but it varies lens to lens.

When I shot images in UV, I sometimes mounted a lens without helicoid.  Then I utilized the Arca-Swiss clamp/plate as a focusing rail, both for focusing in VIS and adjusting the focus shift for UV.
Title: Re: How to remove the coating from a lens?
Post by: ArthurDent on May 13, 2018, 20:52:18
This is an urban myth basically, old and honestly forget about that. There are so many good candidates for UV photography which do not require any such ...

Have a look here on my Blog and you'll find plenty: http://photographyoftheinvisibleworld.blogspot.com/2011/01/uv-lenses-tested-good-for-uv.html (http://photographyoftheinvisibleworld.blogspot.com/2011/01/uv-lenses-tested-good-for-uv.html)

Thank you. I’ve bookmarked your site, very informative! It would seem tto use an enlarging lens, I’d need to couple it to a bellows to get it to focus? So, I’d need rails, bellows and adapters at both ends? Any suggestions?
Title: Re: How to remove the coating from a lens?
Post by: richardHaw on May 14, 2018, 03:22:02
Richard, Do you think ammonia would work on the Nikon 50mm f/1.8 ais? My plan would be to suspend it with the front of the lens pointed down and to use a q tip saturated with ammonia to remove the coating, then use kimwipes to remove any excess, unless there is a better way?

not sure. the coatings on the series E lenses are easier to strip if you want to but I am not sure if you really want to do that. Minolta coatings are known to be soft so you may want to use their lenses instead. just sneeze in front of it and the coatings will fly away like dust  :o :o :o

soak it in strong concentrations of ammonia and citric acid and watch the thing go away after an hour or so. i would just keep the Ais. its too precious to be used for an experiment
Title: Re: How to remove the coating from a lens?
Post by: Macro_Cosmos on May 15, 2018, 06:15:00
Image quality will be drastically reduced if you do that. I suggest buying a lens that works well in the UV range. Bjorn's site has an excellent list  ;D

If you don't mind, it's still a fun project. Keep in mind that some glass elements are actually doped with various substances, rather than coated. These doped glass could affect UV transmission as well.
Title: Re: How to remove the coating from a lens?
Post by: Steven Paulsen on May 16, 2018, 18:19:50
I worked as an optician for many years & I discovered this trick on my own. (Use at your own risk, & this applies to plastic & glass eyeglass lenses.)

The coating always scratched & even flaked off on earlier applied coatings. I removed the lenses from the frame & soaked them for a few hours in common drain cleaner, a mild version of sulfuric acid. It did not effect the hardened scratch coating on common CR39, (plastic,) and no issues on glass, either.

This may work, if you can remove a lens element of your photo lens. I would be cautious of "wiping a lens' If you have a pair of glasses with damaged anti reflective coating, you can bring them back service using the above method.
Title: Re: How to remove the coating from a lens?
Post by: pluton on May 16, 2018, 22:55:17
I removed the lenses from the frame & soaked them for a few hours in common drain cleaner, a mild version of sulfuric acid. It did not effect the hardened scratch coating on common CR39, (plastic,) and no issues on glass, either.
While your experience with using drain cleaner to remove AR coatings is useful knowledge, in the interests of safety and accuracy, I submit to the forum that in the USA, the common drain cleaners are not acidic but strong alkalis, in most cases sodium hydroxide.
MSDS's from two common brands:


Title: Re: How to remove the coating from a lens?
Post by: ArthurDent on May 16, 2018, 23:42:24
While your experience with using drain cleaner to remove AR coatings is useful knowledge, in the interests of safety and accuracy, I submit to the forum that in the USA, the common drain cleaners are not acidic but strong alkalis, in most cases sodium hydroxide.
MSDS's from two common brands:

This is correct. I don’t know how it is done elsewhere, but in America, drain cleaners work by reacting the built up grease with a base (NaOH) in a saponification reaction to form a soap which is easily dissolved with water and flushed down the drain.
Title: Dear Drano Police
Post by: Steven Paulsen on May 17, 2018, 04:45:16
Sorry. I assumed it was all the same. I buy the expensive stuff that is only carried in a few hardware stores. A one quart plastic bottle, with a heavy plastic bag, over wrap. It costs Around $15.00, and lists the active ingredient as sulfuric acid.

I have a mix of copper, iron & pvc in my home. A couple times upon dumping in a small healthy dose, I've gotten a rise of smoke. I am an old, photographer, musician, (long hair, hippy type.) The stuff takes care of hair clogs quickly. (Dump, vacate, wait a minute or two & rinse with cold water. I'll also add, the low cost domestic stuff does the job, on lenses, but not near as fast. (Usually an overnight soak & is fairly useless on bath tub, shower clogs.)


My apologies, and/or, GFY
 8)
Title: Re: Dear Drano Police
Post by: Dr Klaus Schmitt on May 22, 2018, 08:47:56
I still think this approach is not a valid one, gettting a (cheap) UV capable lens does the trick much better....