This is part of a larger series; I’d recommend that everyone read the overview first.
I want to make this clear before I start. The Schott BG40 filter is NOT an ultraviolet-blocking filter. It is designed as an infrared blocking filter, and it works great as such. Seriously- I love this filter. I use it all the time when taking UV photos to block long-wavelength light, and it works in a pinch to convert my full spectrum camera into a visible spectrum camera. I’ll probably do a semi-serious review for the filter eventually.
However, right now, I’m not reviewing it on its own merits. I’m instead reviewing ultraviolet filters. Even though it isn’t an ultraviolet filter, I’m using it as a control for the tests. As such, it’s only fair to judge it by the same standards.
My standards are covered in more detail here, but to sum up:
1- How is the packaging design(0% of total score)?
2: How is the protective case size & durability(5% of total score)?
3- Do the reflections off the glass look off-colour(5% of the total score)?
4- Does it block UV light for my full-spectrum camera(35% of total score)?
5: Does it block any light for my full spectrum camera(10% of total score)?
6: does it block any UV fluorescence from a black light(35% of total score)?
7: How reasonable is the price(10% of the total score)?
So, lets get Judgin’!
1: The packaging: 0 out of 5. The packaging is completely unmemorable, as in I literally cannot remember it. I can’t look at it again, but I’ll get more into that for the next criteria. If Schott had only designed the packaging so that I could recall it from memory five years later, I’d give it a better score. However, as I can’t, it gets a zero. What else could I do? look up photos of the packaging on the internet?
2: The protective case: 5 out of 5. A perfect score! No photos of the protective case, but it protected the lens through my rigorous trials. Well, not my trials, exactly… more like the trials of my dog, who likes to chew on plastics.
The lens survived without a scratch; the case, unfortunately, didn’t. The lens is in another case now, and the old case was given a viking funeral. Vikings were thrown in the trash, weren’t they?
3- Reflections off the filter glass: 3 out of 5.
The lens isn’t shimmery at all. There is no colour distortion in the reflections. However, it is tinted blue, so it gets a pass. They tried something, at least. Now for the nuts and bolts…
4- Blocking UV light from entering my full-spectrum camera: 1 out of 5.
That’s a hard no. Again, this is the control for my tests, and I didn’t expect it to block UV light. In fact, I’d be disappointed if it did.
The Shott BG40 is completely transparent when using my short band pass filter:
It is also transparent when visible light is cut out entirely.
I cheated here: By the criteria of my testing, the UV photograph is supposed to be taken using a Schott BG40 filter and a Schott UG11 filter together. However, I only have one Schott BG40, so I am using the Short Pass Filter in combination with the UG11 instead. It doesn’t change the result, though. The sky might… MIGHT be slightly darker inside the camera filter as compared to outside it. Most of the UV lenses I’ve tested seem to be like that, and I think it is probably just the physical nature of the glass absorbing the UV spectrum, as opposed to any special filter. Even so, I’ll give it a point.
5- Blocking any other light wavelengths: 5 out of 5! Another perfect score!
The Schott BG40 might not be any good at blocking UV light, but it is good at blocking infrared light. It is completely opaque when viewed using my Zomei 680 nm filter. This is exactly what I expected, and is the reason I bought the filter. Partnered with another filter such as the UG11, it allows me to take ultraviolet photographs; on it’s own it isn’t half-bad at converting my full spectrum camera to a normal visible wavelength one(the colours are very slightly skewed towards the red end of the spectrum, but not by much).
I already mentioned the blue tinge to the glass, so it blocks the longer visible wavelengths as well.
6- Blocking UV Florescence: 1 out of 5.
As the BG40 does not block infrared light, I would be disappointed if it had a high score here.
And it gets a 1. It is very faintly darker than on the surrounding paper. I wouldn’t say it is doing a good job. Unfortunately, compared to my other UV filters, it is doing an ‘average’ job. it works about as well as they do.
7- Price: Well… expensive, but I’m judging on how appropriate the price is, not how expensive it is. I think I spent about $60 CDN for mine online, and that was a few years ago. That’s the most expensive out of all the filters I reviewed. Still, it’s a worthwhile filter for my full spectrum camera, so 4 out of 5.
Forty Percent! A failing grade, but how does it rank?
Despite losing points for not technically being a UV blocking filter and not blocking any UV light, the Schott BG40 makes up for lost ground by also not being completely useless and by having a dog-proof case! Schott… you might not block any ultraviolet light, but you’re still getting the bronze medal for UV filters tested! Third Place!
… that means that this is just going to go downhill from here, isn’t it?