How much green does Hoya U-340 leak?

[Stefano]

I just wanted to ask this quick question. I am interested to know if, for example, a 1 mm thick U-340 has still OD 5+ in the visible range or if it leaks enough green to not be considered OD 5. Someone, like Jonathan, has a good spectrometer, and can maybe measure this. I like 1 mm thick U-340 for its high transmission and for the fact that it “includes” light all the way up to 400 nm and doesn’t leak violet (unlike U-360). Hoya provides data only in 10 nm intervals, so my guess can be wrong. I prefer U-340 over UG11 because it has higher UV transmission and lower IR transmission at the same thickness, even if the difference isn’t that big. I know that 1 mm thick U-340 doesn’t leak enough to contaminate a UV image, but my curiosity wins.

[Cadmium]

You can not use U-340 alone for UV-only, you must suppress the IR (Red/IR) with BG (S8612).

Hoya doesn't provide data in the visual range for U-340, however at 1mm thick compared to UG11, U340 will leak some ~550nm~ range light, given that range, no thickness of any BG (S8612) will suppress it.

We have been through this before with your B-410 stack idea, remember?

If you had both U-340 1mm thick and UG11 1mm thick, and you stacked each with S8612 2mm thick, and you held those stacks up to some common household light, you would see a faint image of the light through the U-340 1mm stack.

So, if you use U-340, use 1.5mm or 2mm thick and this will remove the 550nm leak.

If you want to use UG11, then 1mm will work, but I suggest 1.2mm just to be on the safe side and to give it slightly more durability especially if it is not glued to something else.

 

You said: "I know that 1 mm thick U-340 doesn’t leak enough to contaminate a UV image, but my curiosity wins."

Yes it does leak IR like a sieve, and also leaks 550nm. It can't be used alone, and even when stacked it does leak, even if only slightly, there is a difference between U-340 and UG11 when thin.

 

U-360 2mm + S8612 1.5mm top 2mm is what I recommend. No visible. Same with UG1.

However, if you stack U-360 1mm thick (or UG1) with S8612 you will see a very slight faint violet from the light.

 

[Stefano]

Yes, I didn’t write it, but of course you need to block IR. That’s why you needed 8 millimeters of this glass to have UV-only (it was actually a suggestion from me, do you remember?)

[Cadmium]

8mm of U-340 goes back a long ways.

 

The point is, don't use U-340 any thinner than 1.5mm thick, and preferably 2mm.

If you want to go thinner I suggest UG11, it has slightly better visual range suppression than does U-340.

Does that answer your question?

[Stefano]

It is probably better to use thin UG11 + S8612 than thin U-340 + S8612 + BG3. Hoya B-410 is different from BG3. Is there a Schott equivalent for B-410? Hoya has B-370 which is similar to BG3.

[Stefano]

Yes, you said that there is a difference between thin U-340 and thin UG11. I wonder at what thickness that green leak goes below OD 5.

 

This is quoting your last message.

[Stefano]

OD 5 at 2 mm means OD 2.5 at 1 mm. Probably it leaks less than that.

[Cadmium]

I can see the U-340 ~550~ leak at 1mm thick. I can't see it at 1.5mm thick, but I still would use 2mm myself, but I would not use 1mm.

Yes, Schott BG3 and Hoya B-370 are kind of the same, BG3 will suppress visual range more, and transmit UV and IR more.

There is no Schott equivalent of Hoya B-410.

 

[dabateman]

Slightly off topic,

But doesn't 6mm UG5 or u330 also look interesting.

[dabateman]

This combination of 2mm Ug11 with 4.5mm ug1 might also just work. Not too sure how much that IR leakage would look like in images.

[Cadmium]

Off topic indeed, but frankly, none of that looks interesting to me personally, no. Explain why.

[JMC]

Stefano, unfortunately I do not have U-340 in 1mm to test. I do have 2mm, however unless the transmission in your region of interest for the 1mm filter is more than 1% I wont be able to see what is there in my 2mm one, and I would be surprised if it's that high.

[Stefano]

Stefano, unfortunately I do not have U-340 in 1mm to test. I do have 2mm, however unless the transmission in your region of interest for the 1mm filter is more than 1% I wont be able to see what is there in my 2mm one, and I would be surprised if it's that high.

I would be too.

[dabateman]

Off topic indeed, but frankly, none of that looks interesting to me personally, no. Explain why.

 

Oh yes, I did go off without explaining.

From Jonathan discussion with a company, the Ug5 can near Ug11 depending on the batch and lot numbers.

If you play around in the Schott Excel spreadsheet, which I can now do freely as the Android version of Microsoft Excel seems to be free and works with the Schott spreadsheets. You do get to see how similar UG11 and ug5 are. There seems to be at least one chemical ingredient, which ug5 doesn't have that when increased in glass thickness, cuts out the IR peak. As seen with Ug11 but not ug5. This ingredient seems to red shift the ug5 450nm peak component to 500nm roughly, in ug11.

 

So Stefano, when not studying for your finals. Play around some in Excel and you may get an answer. But remember that there are batch and glass lot difference.

 

I got some mixed thickness lot filters and have been playing around to see which I want to finally construct into frames.

[JMC]

David, to be clear for all the explanations that company gave me, I don't for one minute believe that filter is what it was supposed to be or what I ordered. The spectra is too close to UG11 for it to be anything other than that. However the company has now been closed down until this current situation is over, so I cannot go any further with resolving the situation at the moment.

 

Yes there can be variability, but I just cannot believe it can be that big between lots.

[Cadmium]

Although there is a slight IR image in the camera capture using the UG11 1mm,

when looking at this common household visual compact fluorescent bulb with my eyes, through the two stacks, I see nothing with the UG11 1mm x S8612 2mm. I do see the green with my eyes with the U- 340 1mm however.

Here is a comparison between U-340 1mm + S8612 2mm + GG5420 2mm and UG11 1mm + S8612 2mm + GG420 2mm, using the same D7000 UV/IR camera settings, f/4, 1/15s, ISO 3200, hand held.

There is a definite visual range leak different between U-340 1mm and UG11 1mm.

 

U-340 1mm left, UG11 1mm right

[Stefano]

The difference is quite evident. Can you try stacking BG3 with the U-340? I wonder how much it suppresses green.

Do you have BG3 in 1 mm thickness? Above 1.5 mm it should be overkill, since it has OD 4+ in the green region.

[Cadmium]

The thinnest BG3 I have is 1.5mm.