It appears inherent of 365nm led design that apart from the peak around 365nm there is a low intensity broad band of visible light (400nm leds do not have that, and I am testing an LG 385nm led at the moment and it also does not seem to have the problem). Only Nichia found a way to minimise this (but it is not completely absent).
So the visible light problem is not restricted to cheap leds (the expensive Ledengin 365nm led also puts out the whitish light), and a uv-pass filter just fixes it very effectively.
Interested, altho’ I already have a couple of these ordered.
As with a lot of things bought this way, I’m somewhat dubious that we’re getting first quality, rather thinking we may be getting cheaper seconds, but time will tell.
On aliexpress they can be found in various diameters, and can probably be made in any diameter as long as you buy enough of them. I think that for a group buy only 20mm and 18mm could raise enough interest, perhaps 12mm (there will probably not be hoards of people who want their 365nm led in a C8 )
Doing a google search for ZWB2 filters I suddenly came across Gearbest, not sure if there will be a separate group buy price, but they list the 20mm x 2mm ZWB2 filter for $3.99 :-)
Which is good enough for me, ordered one, let's see when it shows up.. (or if it shows up at all, I never know with Gearbest lately, my Olight S1 is still lost and Gearbest does not want to take responsability)
Also doing a Google search for ZWB2 filters, I ended up at DealsMachine. Their price is also $3.99. They are using the same picture as GB.
But I must admit that I’ve never bought anything from them. For the moment I’ll try to over-ride my trigger finger.
For those interested and as indicated in the FastTech deals thread, the UV S2 is available for $ 14.32 and there is a 10% coupon on top of that “XMAS”. https://www.fasttech.com/products/3760700
3 orders and no problem, 4 soon.
You’d better go with the 5 pcs on GB for $5.01.
There is a 20% coupon on DM at the moment “Thanks”, but coupons work the same way as on GB. Anyway there are some good deals ( LG MJ1 4 pack for $ 18.79 ). Be careful, free shipping is not available on all products ( Pana NCR18650B protected 4 pack for $ 14.39 with coupon but $ 6.21 shipping ).