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Filter for Convoy S2+ UV

Fluorescence UV Lighting
7 replies to this topic

#1 Adrian

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Posted 10 August 2018 - 08:35

Has anyone seen this? A remarkably cheap filter to remove residual visible light from a Convoy UV torch.

https://www.banggood...ur_warehouse=CN

I have just ordered one to test it.
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#2 dabateman

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Posted 10 August 2018 - 08:47

Without a spectra, and based on the cost, I would assume that to be a Zwb2 filter.
There has been lots of discussion here about those filters.
When I decided to get a convoy, even though more expensive up front I still think the U340 filter is the best match. You are guaranteed to eliminate all visible. Without that, what would be the point of adding a filter.

#3 Cadmium

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Posted 10 August 2018 - 09:17

Based on the graph they show, see how the transmission crosses the 400nm line into the visible range, ever so slightly, but nonetheless the whole idea of filtering the Nichia LED (used in the Convoy) is to cleanly cut the transmission below 400nm.
This would then be ZWB2, as Da Bateman suggested, the very cheap Chinese imitation of Schott UG1 and Hoya U-360.
Many people think using UG1 or U-360 is better for 365nm, however those don't cut as cleanly below 400nm,
that is why when you filter a UV 365nm torch/LED you should really use U-340 or UG11, because those cut transmission cleanly below 400nm.

Attached Image: U340_1mm_2mm_U360_2mm_UG1_2mm.jpg

Edited by Cadmium, 10 August 2018 - 09:39.


#4 Andrea B.

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Posted 10 August 2018 - 19:00

Banggood's own chart (attached) shows violet transmission between 400 - 410 nm, approximately.

So how can they say this: "Can filter all the stray light and keep only the 365nm UV light" ??
:o :rolleyes: :lol:

Attached Image: banggoodChart.jpg
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#5 Andy Perrin

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Posted 10 August 2018 - 19:44

What is the output of the torch at 400nm+?

#6 JCDowdy

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Posted 10 August 2018 - 19:50

View PostAndy Perrin, on 10 August 2018 - 19:44, said:

What is the output of the torch at 400nm+?

Here is the irrradiance spectrum

#7 Cadmium

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Posted 10 August 2018 - 19:56

First of all, I don't trust the charts I see for the cheap Chinese filter glass.
It is possible that filtering the Nichia 365nm LED with either U-340 or U-360 would probably be cutting some of the blue leak,
however, technically if you are going to go to the trouble of filtering the torch, then it should be filtered below 400nm completely.
I have seen on other forums people talking about filtering with 360nm glass (UG1, U-360, 'ZWB2'), but those don't cut below 400nm.
When I compare the graphs, I don't see much benefit of using 360nm glass rather than 340nm glass (UG11, U-340, 'ZWB1').
Personally, I would use a 340nm glass.

#8 Andy Perrin

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Posted 10 August 2018 - 20:01

View PostJCDowdy, on 10 August 2018 - 19:50, said:

So from that it looks like 2mm UG11 takes you down 2+ orders of magnitude, which presumably is good enough. The ZWB seems to have 5% transmission at 400nm, which 1.3 orders. (Even if you trust the chart...)

Edited by Andy Perrin, 10 August 2018 - 20:02.