UV pass glass - looking for info

[Guest]

Hi,

 

I found this UV-pass glass online and am just wondering if anyone knows of it already, what its transmission profile is, etc.

 

Found here: https://uvsystems.com/store/product.php?productid=16145&cat=5&page=1

 

Thanks,

- Mark

[Andy Perrin]

I think this is the same as the FL-20, but with different filter dimensions? They give the spectrum here:

http://www.uvsystems...nsmission_1.pdf

 

Big infrared leak, which is no surprise. Some visible leakage also, if you consider UV to start at 400nm and smaller.

[Cadmium]

It might work OK for fluorescing objects, but I suspect it has hidden visual range transmission, beyond just the 420nm, more like Hoya U-325c (similar to U-330) sometimes used for filtering lights for fluorescence.

If it is intended to be used for that kind of lamp filtration then it is possible it is a similar kind of animal.

Neither U-330 nor U-325a would be considered UV-only, even when the IR is suppressed they both have a lot of visual transmission, which is of course great for UV+Blue+Green stacks, but not for UV-only stacks.

The FL-20 graph looks a bit different however, a little hard to tell from the linear graph.

[Guest]

I don't know how I missed that link on their site. Thank you for finding it.

 

This glass should work very well for my intentions, as I'm looking for a large filter for UVIVF imaging. It seems that many common things seems to fluoresce not only under UV, but also blue light - so the fact that this glass leaks into deep blue/violet is actually something of a bonus. And I'm not worried about the strong IR leak, since I'll be using a stock camera (which of course, has its own internal IR cut filter). Also, I'm not too worried about the leaked IR causing any fluorescence of its own, since that would likely be even further into IR (which again, the internal cut filter would block). And the chances of stumbling across some anti-stokes fluorescence are very slim. And that any anti-stokes fluorescence would be of strong enough signal to even be picked out above the VIS signal is even less likely. So I feel good about this. I think it will be a good, low cost option for a large filter area.

 

Thanks again for finding that transmission profile.

[Andrea B.]

But Mark if your UV induces violet/blue visible fluorescence you won't know whether you are seeing that or reflected violet/blue light if you use filters with violet/blue leakage?

 

Also note that internal cut filters are not always optimal. In older cameras or compact cameras, the internal filters may actually be rather weak.

[Cadmium]

Andrea is right. It is best to use 365nm light for UVIVF excitation. I have seen 400nm LED lights excite visual fluorescence also, but then you can't separate the visual blue light from visual blue fluorescence.

I recommend using narrow band 365nm light, filtering the light with something that blocks any transmission above 400nm, and also filtering the camera lens with something that blocks anything below 420nm.

You can't trust a stock sensor filter to block UV.

[Guest]

I completely agree with both of you. But, I am actually looking to filter out blue fluorescence (on camera filtration).

 

My only reason for this, admittedly, is... lint. Yes, lint. In indoor settings it seems to be everywhere. Floating, settling, brightly fluorescing in overpowering intrusions to dominate my fluorescence photos!

 

Its a bit annoying.

 

So, UV + deep blue/violet works for me. I get a wider excitation wavelength range, thus a wider potential range of fluorescence in the higher wavelengths, without all those lint invaders blowing out specks and spots all over my images. I already know laundry detergents typically add brightening agents, so I'm not really interested in photographing that fluorescence (from the lint dust generated with practically every movement we make).

 

All I need now is to find a good on camera filter to cut-on at just the point where this glass cuts-off.

[rfcurry]

Mark,

 

You might try the Schott KV series (see http://www.itos.de/en/schott-optische-filter/interference-and-special-filters/kv-filters/ )

I use the KV408.

[Andrea B.]

Canned air to delint a subject can be useful. As long as you don't blast the subject to smithereens. Some of those canned airs thingies are way powerful!

 

But fluorescent lint is why the adobegeeks invented the Healing Brush.

 

Shooting fluorescence is lots of fun. We will be looking forward to your results.

[Cadmium]

As far as I know, Schott discontinued making the KV filters a few years ago and now there may only be a few left of different ones. Most are not available.

[rfcurry]

This site claims to have some.www.itos.de/en/schott-optische-filter/interference-and-special-filters/kv-filters

 

[Cadmium]

I don't think Schott still makes those. I checked with that site and they do still have some in 'limited numbers'.

[JCDowdy]

I found this UV-pass glass online and am just wondering if anyone knows of it already, what its transmission profile is, etc.

Found here: https://uvsystems.co...45&cat=5&page=1

 

Judging by the transmission curve shown on the UVSystems site I think it might be a Hoya FL-W

[Cadmium]

John, But the lowest transmission of Hoya FL-W is 40%, much higher than that shown on the graph Andy linked to above. Maybe you have found some other graph on UVSystems site?

http://www.uvsystems.com/specs/filters/

[JCDowdy]

John, But the lowest transmission of Hoya FL-W is 40%, much higher than that shown on the graph Andy linked to above. Maybe you have found some other graph on UVSystems site?

http://www.uvsystems.../specs/filters/

 

Yeah, it is not exactly the same. I was asuming the UVSystems FL-20 LW filter was much thicker than the Hoya FL-W but it looks like the difference is more than thickness alone.

[Cadmium]

Yeah, Well if it were the same glass then the peak transmission would be much lower for thicker glass.

 

As far as KV filters, Schott stopped making those several years ago given the limited market and they are not RoHS compliant.

So what is left out there is all that is left, they will not make more, and Schott's stock is gone.