Holmium oxide glass?

[Fandyus]

So I ran into this on Ali, I would say it's rather expensive but as far as filters go, it's pretty normal. But as far as Ali sellers go, it's quite pricey for sure. It's supposed to be holmium oxide glass, what would this be used for? And what effects do you guys wager it would have on a full spectrum camera?

https://a.aliexpress.com/_mPqyZKF

[Cadmium]

It looks like it suppresses a part of the blue spectrum.

I think it is used for calibration, such as spectrometers.

I don't know how it might be used for photography, other than like I said, the suppression of that blue.

[Andy Perrin]

I think Cadmium nailed it. It's not meant for photography, and if you want a long pass filter, there are better options.

[Fandyus]

Thank you guys. I totally understand it's probably not meant for photography. But it does come in a filter thread that would imply some people mount this on their cameras, unless I'm wrongly assuming that such filter threads are only used for lenses.

[colinbm]

So I ran into this on Ali, I would say it's rather expensive but as far as filters go, it's pretty normal. But as far as Ali sellers go, it's quite pricey for sure. It's supposed to be holmium oxide glass, what would this be used for? And what effects do you guys wager it would have on a full spectrum camera?

https://a.aliexpress.com/_mPqyZKF

 

To me it is just a 300nm long pass filter on a full spectrum digital camera ?

It is blocking the cyan, no problems, a full spectrum digital camera doesn't see cyan, it is a response of the blue & green channel, so it will still make a cyan image.

[Andy Perrin]

Thank you guys. I totally understand it's probably not meant for photography. But it does come in a filter thread that would imply some people mount this on their cameras, unless I'm wrongly assuming that such filter threads are only used for lenses.

I think the latter in fact. There are also such things as hyperspectral cameras that generate a spectrum at each pixel, so that is also a possibility.

[dabateman]

That looks like a filter you could use to knock down the blue spike from a white Led light. It should even out a warm white led if I am remembering the spectrum correctly.

 

I wonder if they are working on negative white led filters for Astrophotography now. The minus Mercury filters work very well to reduce the Mercury line spikes. A Mercury bulb looks good and even with one of those filters.

 

This filter may do the same for white led bulbs.

[Andy Perrin]

Nah, there's nothing to be done about white LED pollution really. The astro community uses very narrow H-alpha filters but then all you get is H-alpha and it still won't work in a city. I asked one of the top astro guys (Sebastian Volmer) and he said, the solution to light pollution is to go to a darker place, if you can find one (I paraphrase). In the western US it's actually not that hard to find dark skies if you go a few miles out of town. One of my friends actually captured a Milky Way as a two exposure composite on the same night OVER Los Angeles, with the help of some conveniently reflective clouds and a great vantage point outside town. You can't do that sort of thing on the east coast US!

[Cadmium]

I think I would get a spectrometer first...

https://www.perkinel...andard-n1010545

[Andy Perrin]

I think I would get a spectrometer first...

https://www.perkinel...andard-n1010545

 

Like Dorothy Parker almost said,

 

Why is it no one ever sent me yet

One perfect spectrometer, do you suppose?

Ah no, it's always just my luck to get

One perfect rose.

[dabateman]

Interesting USP<857> still says to calibrate the spectrometer using a solution. But the revised USP<851> indicates that a suitable glass filters can be used for wavelength calibration.

But does indicate that a solution of Holmium oxide following USP<29> is better than optical filter.

 

So little wiggle room added there.

[ulf]

The holmium glass is mostly used as a calibration reference for some types of spectrophotometers.

If the instrument is designed to have samples inserted in slits or holes like for kyvets, it is sometimes not possible to use the line spectra from a calibration lamp for calibration.

Then a holmium glass can be a good calibration source.

Cadmium linked to a good example for that above.

 

I think that didymium-glass might be used in a similar way, but maybe it is not wavelength-wise as stable.

 

Didymium glass has more different uses than holmium glass.

 

It has been used in goggles for working with hot glass.

Then there is often bright light emitted, typical for the sodium lines around 589nm

https://www.chem.uci...s/RWFSodium.pdf

Didymium glass has a good rejection of that light.

 

When the majority of light pollution from cities came from the yellow light from low pressure sodium lamps, didymium filters could be used to improve some types of astronomic pictures.

When those lamps was replaced by LED-lamps that function of the filter-glass became obsolete.

 

Didymium glass has also been used in several types of "Enhancing/Intensifying"-filters. The most known is the Red Enhancer.

Similar types of glass filters with some variations in transmission, having with different levels of cancelation and tint ha been sold as blue- and green-enhancers.

 

I had a period when I gathered many different types of filters to hone my ability to measure filters with my spectrometer.

In that collection I have some different types of enhancing/Intensifying-filters. I have never used them for photography.

[JCDowdy]

Holmium reference cells are used to document performance of spectrophotometers.

See: Holmium Glass Reference for Wavelength in the UV/Visible For assessing the wavelength accuracy of your spectrophotometer

[Andrea B.]

(Andy, made me laugh!) :lol:

[Andrea B.]

BTW, did I remember that Holmium is a actual element, #67 ?? No, I did not !! :lol:

When I saw Fandyus’ post about the holmium oxide filter, I had to go look everything up.

(I learn so much here!!)

 

Anyway, while furthering my education, I read that holmium oxide is somewhat toxic.

And that you shouldn’t handle the glass fragments if such a filter breaks unless you are wearing puncture proof gloves.

So there’s that.

[Andy Perrin]

BTW, did I remember that Holmium is a actual element, #67 ?? No, I did not !! :lol:

Wait, are you saying that Holmium is...elementary, my dear Andrea?

[ulf]

Wait, are you saying that Holmium is...elementary, my dear Andrea?

No that was Holmes. "Elementary, my dear Watson", not.

https://quoteinvestigator.com/2016/07/14/watson/

[enricosavazzi]

It looks like it suppresses a part of the blue spectrum.

I think it is used for calibration, such as spectrometers.

I don't know how it might be used for photography, other than like I said, the suppression of that blue.

Aside for blocking blue in a general sense, holmium has several very sharp absorption peaks, which make it useful for spectroscope calibration.

 

It is not just holmium oxide but e.g. a holmium perchlorate solution, which looks even better in term of sharp absorption peaks (but of course not practical for making solid filters out of it): https://www.starnacells.com/d_ref/d_wl/HL.html . Perhaps this is a general property of holmium ions (or of a specific holmium ion), so it does not matter much whether the ions are dispersed in glass or a water solution.

[Andrea B.]

Most Excellent Punnery Award 2021 goes to ……. Andy Perrin!!

[Fandyus]

BTW, did I remember that Holmium is a actual element, #67 ?? No, I did not !! :lol:

When I saw Fandyus’ post about the holmium oxide filter, I had to go look everything up.

(I learn so much here!!)

 

Anyway, while furthering my education, I read that holmium oxide is somewhat toxic.

And that you shouldn’t handle the glass fragments if such a filter breaks unless you are wearing puncture proof gloves.

So there’s that.

I'm glad you learned something new. Speaking of toxicity, how toxic are the oxide layers that from time to time create a coating on top of our filters? Did anyone ever explore that?

[Andy Perrin]

Probably shouldn’t lick your filters, Fandyus. S8612 is a bunch of stuff, mostly nontoxic, except for a tiny smidge of arsenic (<1%). I don’t know how much arsenic is poisonous but like I said, don’t lick them.

[Cadmium]

https://www.schott.com/d/advanced_optics/c7ec8c94-eef9-4da7-8506-c26483555fdf/S8612_SDS_EN_V5.2_202003.pdf?tenant=ao-cert

[dabateman]

Material safety data sheets are a good worst case source for protection information.

I remember the one for sodium chloride used to be quite extreme. Recommended always wearing gloves, face covering to avoid dust inhalation and safety shoes with out open toes.

Sodium chloride is common table salt.

 

We also had one for dihydrogen monoxide to scare people, when I used to manage those for a company way back. That substance causes significant number of deaths each year. But seems unavoidable.

[Andy Perrin]

 

We also had one for dihydrogen monoxide to scare people, when I used to manage those for a company way back. That substance causes significant number of deaths each year. But seems unavoidable.

 

Too much of a good thing.

[dabateman]

Another word of caution that just popped into my head.

 

Serious problems can be in the exposure time and frequency. I friend of mine was working in manufacturing in University. What he was handling was generally safe. But not for 6 hours a day 5 days a week for one month. He got severe cobalt poisoning.

 

So think smart about what you are doing and how you exposure yourself.