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UltravioletPhotography

Polished off UV coating?


Arti

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I did this once on an old 28 mm Vivitar lens. It was a long and difficult process of what seemed like endless polishing with a sapphire paste. While the polishing results were good - the coating was removed, the imaging result was poor - images became hazy, and UV transmission was actually slightly decreased. Definitely the opposite of what I had hoped/expected.

 

I only have low res versions of these old photos (unfortunately I don't have the originals saved anywhere). In this test, the image on the left shows the UV image produced with the original lens before modification (i.e., removal of the lens coating). The image on the right is an equivalent exposure after removing the lens coating.

 

 

Here is another test with the same lens. This time I included a pair of safety glasses to show UV absorption (i.e., to ensure it was a "UV image"). Again, original/coated lens image is on the left, modified/uncoated on the right.

 

 

I would not recommend doing this. Ideally of course, a UV lens would have an AR coating designed specifically for UV wavebands.

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I bought a mint condition Wollensak 25mm f1.5 c-mount lens, which wasn't very sensitive to uv. So I took apart all 4 elements of the lens and polished them with this.

https://www.ebay.com/itm/Cerium-Oxide-Filter-Glass-Polishing-Compound-Professional-White-Optical-Grade/293113309500?hash=item443eea293c:g:Gv8AAOSwqSRc-R7P

 

That dramatically increased the UV usefulness of the lens. But this was previously known as a good UV lens.

This may not work for other lenses. It does depend on what glass is used in their construction. There are many different types of optical glass used in lenses.

 

 

 

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Birna use to polish off the lens coating of the Nikon E lenses.

Cerium Oxide will do that.

 

Here it is:

http://www.naturfoto...V_IR_rev05.html

That is an old page.

Last update 26 July, 2004

 

Some of the information is outdated and partially incorrect, but not about removing the outer AR-coating.

I'm sure Birna have knowledge about this that is more up to date now.

 

Polishing might help if the glass isn't scratched in the process.

Even without scratching the surfaces the added surface reflexes can cause other problem.

If the used optical glass types transmit UV and isn't too thick you might improve the transmission.

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Ulf, I was responding to Arti's question, and Birna's page about doing such a thing was the only example I could think of.

Sorry that page is so old. :smile:

Perhaps you can PM Birna and ask for more details or updates, I am not the one to ask, I have never tried removing the coatings on any lens, and I don't plan to, however, Arti has a very interesting question.

I have a 35mm E, and a 28mm E, they will work for UV without removing the coating (although there are other inexpensive lenses that work better).

 

You could get some inexpensive lens and try out the idea, test the lens before/after to see what the difference might be.

I think if I attempted such a thing, I would remove the front element if convenient, so that polishing could be done separate from the lens body to avoid getting any polishing compounds into the lens.

I like your question, and that page was the only link I could think of pertaining to such an idea. Maybe ask Birna, it seems like a valid idea to me, but I would proceed with caution.

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I second Marks opinion above.

 

I would only do it for the fun of the exercise it self if I had enough time to waste.

The result can go either way.

You can destroy or making a lens's function worse even if you might improve the UV-transmission slightly.

See the added glare in Marks images from the polished lens above.

It definitely transmit more UV, but is still useless IMHO.

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  • 2 weeks later...
enricosavazzi

That is an old page.

Last update 26 July, 2004

 

Some of the information is outdated and partially incorrect, but not about removing the outer AR-coating.

I'm sure Birna have knowledge about this that is more up to date now.

 

Polishing might help if the glass isn't scratched in the process.

Even without scratching the surfaces the added surface reflexes can cause other problem.

If the used optical glass types transmit UV and isn't too thick you might improve the transmission.

Several years ago I - kind of - followed those instructions and removed the front coating from a Nikkor Series E 35 mm lens with cerium oxide. At least in my case, the result was that the coating came off first along (pre-existing?) micro-scratches on the lens surface, then the glass underneath these scratches abraded much faster than the surrounding coated "islands". The coating is apparently much harder than the lens glass. I ended up with an extreme "soft-focus" lens that convincingly emulated the results one should expect from using the bottom of a wine flask instead of a camera lens.

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  • 2 weeks later...

Several years ago I - kind of - followed those instructions and removed the front coating from a Nikkor Series E 35 mm lens with cerium oxide. At least in my case, the result was that the coating came off first along (pre-existing?) micro-scratches on the lens surface, then the glass underneath these scratches abraded much faster than the surrounding coated "islands". The coating is apparently much harder than the lens glass. I ended up with an extreme "soft-focus" lens that convincingly emulated the results one should expect from using the bottom of a wine flask instead of a camera lens.

That doesn't look good. I have a bunch of old and new lenses that I am willing to givit a go but, this is useful info thanksmate. I might probably find who has the less strength of coating and start with it first

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I haven't tried to polish-off the coatings off a lens yet....But....

I was wondering....if a plaster cast was made of each half of the lens, the polishing compound could be applied to the lens & the lens placed into the cast & the lens moved around in the cast, so it would polish the lens without loosing its shape....?

How does this sound...?

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I don't think you are going to significantly change the shape of a lens by just polishing the coating off. If you do then you are working too hard on it or using some machine.

The issues come with exact alignment of the elements, not just flipped, but exactly ticked as removed. If you can draw a thin line down the outside of the lens metal barrel. Then as you remove an element, carefully, if possible mark a hair line with graphite on the edge to its exact orientation from the lens. If you can't mark an element, carefully place it on a marked soft lens cloth, keeping the orientation from the barrel.

The orientation can matter and affect the final image quality. Off center lenses can also be a problem, when placeing each element back, make sure it sits as it was or adjust it to be more in line. There are little suction cup thongs that people use to carefully sit and position a lens. But I just make sure to wear gloves and move slower than seems comfortable. As in crossing the street in 3 light cycles.

You can make it worst or better by not realigning everything correctly.

 

Or you can just have fun and flip elements around, changing the optical quality and creating interesting effects. There are many people that rediscovered that old trick. Maybe 2 PetaPixel posts about it.

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I was just thinking of this plaster cast idea as some have said they ended up with uneven patches with the coating....?

 

By-the-way Dave I now have a SD Quattro....:-)

Col

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I was just thinking of this plaster cast idea as some have said they ended up with uneven patches with the coating....?

 

By-the-way Dave I now have a SD Quattro....:-)

Col

 

Cool, did you get an SD or the SDH?

I loved the handling of that camera when I rented it. The best fit for my hands. Also was the best monochrome camera that I have ever used. Its the only monochrome digital camera I have ever used, but still great.

On my rental, the exposure meter didn't work well with the intended internal UV/IR block filter, was all over the place.

However, it work perfectly fine either without any in monochrome mode or with a BW 486 filter. So was better that way.

Have fun with it, the Small mode is just like the old Foveon with equal resolution to all layers.

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Thanks Dave

I got it for the mono & UV ability first & for the Foveon which I am a fan of, I'll learn the IR again too.

I like resolution without the 'nutella'....;-)

I really want to try the Sigma fp for UV but the second-hand market has to come down considerably before I try it.

I want to see if I can utilize the space that was for the mirror for inserting smaller filters, like 40mm or so...

Sorry, I just got the SD as the SDH is double the money for not much pixel difference ?

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Actually in year 2020 hindsight must say its not the only digital monochrome camera I have used. I got to play with a Phase one 260 monochrome camera years ago. But that was only for a day. The thing was huge.

Depending on how the future Sigma Foveon looks I may get a SDh down the road. I was tempted at $750 at KEH, but didn't grab it. I like to get my cameras around $400 to $500. Only exceptions were my first DSLR, the Olympus E3 which I bought new for a staggering $2300 and my Nikon DF which I got for $1200.

 

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What do telescope lens makers use to polish their lenses? I had a friend once who was polishing a telescope lens but I don't remember what he was using?
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