Quick question - is ZWB3 really passing UV from about 230nm?

[lukaszgryglicki]

Hi, I've came across this https://www.etsy.com/uk/listing/602785273/zwb3-ug5-u330-2537nm-254nm-uv-pass

This even reports "253.7nm" as one of possible usage. Did anyone ever testes ZWB3 glass for passing from 230 to 280nm?

I ask ebcaus eif it really does that I could (in theory) buy a filter 15mm thick and use it alone as low pressury mercury lamp filter - the holy grail I'm looking for - pass UV < 280nm and block UV-B, UV-A, Vis, NIR...

 

[colinbm]

NO, not even 254nm @ 2mm thick.

 

 

[lukaszgryglicki]

OK thanks for quick reply, so the transmission spectra is just a typical lie? 

[colinbm]

I can't speak for the Chinese.
This is what I get for ZWB3 x 2mm, with my spectroscope, using a 254nm fluor lamp. It is not showing the left of the bottom of the bell curve because it is irrelevant.

[lukaszgryglicki]

OK thanks for confirming, I was quite sure it is not possible, but I wanted confirmation.

So a word of warning for anybody looking for 253.7nm pass filters - all those based on ZWB3 are fake.

 

[colinbm]

@lukaszgryglicki No you can't say that. They can be batch specific too.

[colinbm]

I'll do some more tests on the latest that I got from China & some Hoya that should arrive next week.

[lukaszgryglicki]

WOW, thanks a lot, I wonder if this is possible that some pass below 280nm and other don't - but in any case - I would need really thick one to filter out other wavelengths, I mean it should at least pass a lot more in my desired band than out of band. Only then using thicker glass would make sense for separating my band.

 

[JMC]

My experience with ZWB3 is that is does pass 254nm at typical thickness (I have one marked ZWB3 at 1.5mm thick from Igor who used to supply UV lenses and filters on ebay). Transmission shown here;

https://www.ultravioletphotography.com/content/index.php?/topic/1313-filter-transmission-charts-1/&do=findComment&comment=17214

It has a visible leak as well, and of course significant IR transmission.

Not sure below 250nm I can't go that low.

ZWB3 is claimed to be like Schott UG5, which can also transmit below 250nm (depending on thickness) and has the same type of visible leak and IR transmission.

[lukaszgryglicki]

Yeah, I'm still looking for something that would pass mercury line 253.7 and block everything else, but maybe I can focus on just blocking other mercury lines longer than 280nm, so maybe OD blocking should be maximum around those other lines - the ultimate goal is to be able to use low pressure mercury lamp light as the only light (total darkness with lpHg lamp) and then register ONLY < 280nm... after so long time I still don't know how to do this.

 

[ulf]

Your problem will be blocking everything else.

The ZWB3 has a very big transmission bump around 700nm that will not reach any useful OD even with thicker glass.

That will not work as you want it to do!

 

I have ZWB3 2.0mm, 2.5mm and 3.0mm

I think I can do a more proper pure transmission measurement from 200nm with my deuterium light source.

 

I am convinced that Colin's measurement setup is not able to do that properly.

He is showing the combination of his light source and the filter and I suspect it is not quire correct.

We have seen before that his spectrophotometer is truncating some result when it gets too marginal.

[lukaszgryglicki]

Well "blocking everything else" *is* my biggest issue for a long time already, I don't have a solution yet.

 

[dabateman]

My zwb3 does pass the 254nm peak, but it doesn't block much. Its not what you would want to be specific for 254nm. 

Using the Schott Excel spreadsheet,  the 250nm peak seems matched with the IR. To reduce IR over 20mm thick, the 250nm edge is gone. 

[lukaszgryglicki]

So sad. Any reccomendation for 253.7nm only?

 

[rfcurry]

Lukas,
Have you already checked the Knight Optical filters, specifically the https://www.knightoptical.com/stock/default/254nm-interference-bandpass-filter-12-5diax12nmbw.html ?

 

[lukaszgryglicki]

I'll send them RFQ, but it looks typical "average OD4" - this usually means that there is OD3 around 700nm sometimes in diofferent wavelengths.

I would prefer to see "minimum blocking OD5". Also many of such filters are only specifying blocking when light is ideally at 90 degrees to the filter surface - which is not true when uysing for photography and is a *real* problem, I can *see* through Edmund's 254nm bandpass filter if I look at the angle...

Thanks, RFQ sent, will see and report here.

 

[Andy Perrin]

According to Jonathan's tests, the Sirchie KrimeSite filter for 253.7nm is among the best he found.

[lukaszgryglicki]

Can you paste a link to such a filter "Sirchie KrimeSite filter for 253.7nm"? I can't find it - is this avail in 52x0.75mm filter thread or maybe just a circular filter at least 50mm in diameter?

 

 

[JMC]

The ones we got at the time were in second hand items, and unfortunately no makers markings on the filters. The consensus was that they 'looked like' they were made by Omega in the US, although as far as I am aware that was never confirmed. They were 25mm diameter ones. While they had good blocking of visible and IR, the UV transmission was relatively low at around 20%.

[lukaszgryglicki]

This is perfectly OK to pass 20% at 253.7nm while maintaining OD5.5+ blocking of everything else. now the problem is:

- Are they color filters or interference filters? The second are not good for photography as their OD rating differs A LOT depending on AOI (angle of incidence) - I can see this very painfully with my interference EdmundOptics filter for 254nm.

- Can I get ANY in a standard 52x0.75mm filter thread or with some extra adapter?

 

[JMC]

They are dichroic filters, so there will be some change in transmission with angle. I can't measure anything to an accuracy of between than OD4, so below that I have no idea. I would presume these would be a custom request to get one that size. Try Omega filters in the US with your needs maybe? https://www.omegafilters.com/

[lukaszgryglicki]

Well, Omega never responed to my RFQs... :-(

 

[rfcurry]

Okay, Lukas, what is wrong with the Asahi ZBPA524? It gives 26% peak and comes in 50x50mm.
Here is the curve from data from their website -  https://www.asahi-spectra.com/opticalfilters/detail.asp?key=ZBPA254 :

 

 

[lukaszgryglicki]

Looks promising but I'm a bit concerned with "Angle of Incidence (AOI): 0 degree (CWL shifts if the AOI changes.)" - I will ask them if this filter is interference based or colour glass filter type. Will also need OD5+ blocking so I guiess it would have to be 20%-30% thicker and mounted in 52x0.75mm filter thread.

 

[rfcurry]

Lukas,

 

You are requiring impossible parameters. It is like asking for the OED, with all 13 volumes in one, large-print, pocket-sized, and on India paper.

That is an interference filter. It says the substrate is Fused Silica. If you want to get a good AOI, just mount the filter at the back of the lens, where the light is nearly collimated. Interference-based is the only way you can get what you want, no ionic glass has been made to accomplish it; trust me, I spent months looking for glass for you. Why do you need OD5+: you are providing the UVC light source, you can minimize Visible and NIR intrusion.

I guess I don't understand. I wish you all the best in your search.

 

P.S. - you can always stack interference filters to get the OD you require.