 Believe it or not, light pollution filters, like this one, are increasingly a controversial topic among astrophotographers, with some claiming they are a complete waste of money, and others saying they wouldn't leave the house without one. Instead of just injecting yet another opinion into the foray, I thought it would be better to do an exhaustive review of four popular light pollution filters under different sky conditions, and with different kinds of cameras, and share all of my test results, and that way you can decide for yourself whether or not a light pollution filter would be worth a purchase. Hello, my name is Nico Carver, and my main website is nebulaphotos.com. Today, I am also announcing a new website to go with this video, which is astrophilters.com, where I will just be releasing test results and reviews of astronomical filters. The link is in the description, of course, if you wanna check it out. This video was suggested and paid for by my patrons over on Patreon. If you wanna join us, it starts at just $1 per month. So the purpose of this video, again, is to do in-depth reviews of four filters. We have the Optalong L Pro, the Astronomix CLS, the SV Bony CLS, and the Bader Neodymium. And I'll be testing them with various instruments, including a spectrophotometer, a small telescope, and an unmodified DSLR, and finally, a dedicated astronomy camera. And my goal with doing all of these tests is to give you information needed to make up your own mind about using these kinds of filters and to pick one out. A few notes, all my real-world testing was done with a telescope on an equatorial mount with these cameras attached to it. I don't recommend buying a filter for what we call untracked astrophotography, meaning astrophotography on a fixed tripod. And you can find my reasoning for that in my video simply titled, Filters for Deep Sky Astrophotography. Of course, the link is in the description. Before we jump into the tests, one more thing. Since this is my first full review on the channel, I just wanna let you know that I'm also publishing a review policy on my websites and also as a video. So feel free to check that out if you're interested. And part of that policy is to disclose where I got everything for my reviews. So let's do that for this video. I purchased all of these filters for this review as well as the equipment needed to make the spectrophotometer using proceeds from my Patreon. The Canon 5D Mark III, the telescope and the mount were things I already owned. And the QHY-168C is on long-term loan from QHY directly. So next up, we have the tests. I do use the chapters feature for the YouTube timeline. So if you ever wanna skip ahead, please feel free. So part of the reason this review ended up taking so long is because I got into my head that I wanted to verify the spectral transmission of all the filters that I was reviewing, which took a long time to get that process sorted out with all the equipment that I needed. But I did figure it out and I'll just explain the process that I use quickly here. I start by calibrating my spectrometer and the software using a neon bulb because neon has very distinct spectral emission lines. So it's easy to calibrate against those because we know exactly where those should fall along the spectrum. I then use a quartz tungsten halogen bulb from Thor Labs to shine light through the different filters and understand where they're notching out different parts of the visible spectrum. This little photometer attachment is something I put together and then the light goes through a fibroptic cable into the spectrometer and then through a USB cable out to the computer where I'm using Theramino software to analyze the spectrum of the different filters. And here are the results. So this is the Oplong L-PRO's published transmission curve and then this filled in area is what I discovered. And one note here before we go on to the next one because of the way that a tungsten halogen bulb emits light, it's not very sensitive in the blues, especially the deep blues. So I'm only confident in my curve from about 450 nanometers up, so I just cut it off at that point, anything below that because it just wasn't reliable data. But anything above that looked quite reliable and so I am confident in my results. But keep in mind that these are my particular filters that I'm testing. So I'm really just testing the published results that these companies put out versus my particular filters. Your particular filters might be different but this sort of is a quality check on the filters to see how closely they align with what has been published. And for the most part they did very well. So anyways, here's the Oplong L-PRO versus what mine showed. And the only real note here is that they didn't publish that there is a little bump of IR around 800 nanometers. I don't think that would have any effect on imaging because most commercial sensors would have very low quantum efficiency up there in that range. So I wouldn't worry about it, but I did find that it had a little IR bump out there. All right, here's the Bader neodymium. And then here is what mine looked like and it was incredibly close to what they published. The only thing was that it cut off maybe a little bit sooner than what they published and I thought that the O3 transmission was actually a little bit higher than what they published. They said it would be around 85% and I found it was more around 90%, which is good. Here's the published Astronomix CLS. And here's what I found. They said the notch started at around 540 nanometers and in my test it looked like it started more like around 550 nanometers, but pretty close, close enough that I'd say it's pretty accurate. And here's the SV Bony CLS. This is what they've published. And just like the Astronomix CLS, they said that the big notch would start at around 520 nanometers and my reading was about 10 nanometers off from that. It started around 530. And then on this one, also where the notch ended was also a little bit off. So my filters seem to have a slightly narrower notch than what was published, but that's perfectly fine because it's still cutting out most of that yellow spectrum that most light pollution filters are targeting. I should say that the Astronomix CLS is not an IR cut filter. So keep that in mind if you're using a modified camera or an astronomy camera. It does not block the IR, but if you're using it with the DSLR, then that wouldn't matter. And same thing with the SV Bony CLS. It's basically a very similar filter to the Astronomix. It doesn't block the IR, but it did seem to have lower IR transmission than the Astronomix, which was interesting. Okay, let's jump into physical characteristics of these filters. Starting with the Optalong L Pro. This is what the box looks like. And if you open it up, it comes with a nice transmission chart and a plain box for the filter. This is my preferred kind of filter box. Comes right out. It is a two inch filter, as all the ones I'm reviewing are. Has minimal knurling on the top. It measures five millimeters without the threads and about 6.8 millimeters with them. It does have the little notches on the inner filter ring. So if you do have a spanner like I do, you can take the filter apart and measure the actual glass filter inside. It measured about 45 millimeters across or 1.8 inches. Here's the Bader Moon and Skyglow Neodymium. It has a nice packaging, but I don't really like the wax paper thing that it comes in. I'd probably lose that. And then the filter just bangs around in the box. So not my favorite inside the package. It has really nice knurling, both on the sides and on the top. Again, 48 millimeter threads, two inch filter. It's the thickest of the filters that I reviewed at about 5.91 millimeters without the threads and about 7.87 millimeters with the threads. Here's the Astronomix CLS. It's the only one that has the nice gold foil quality sticker. So you know that it hasn't been tampered. Here's the inside. It has the red foam insert, which is typical of Astronomix. I like this kind of box again. The Astronomix, like the L-Pro, has minimal knurling just on the top. It is the thinnest of all the filters that I looked at at 4.4 millimeters above the filter threads. And 6.8 if you include them. Here's the SB Bony CLS box. Very plain, very plain packaging all around. It seems to use the exact same filter mounting as the Optalong, so minimal knurling on the top, smooth finish around the edge. And it is about 5 millimeters above the threads and 6.7 millimeters with them. Okay, now let's jump into the actual real-world tests starting with Bortle 4 with a stock DSLR. And some of you may be wondering, why is tested Bortle 4 that's not light polluted? Well, to some people it is. If you're used to very, very dark skies, then Bortle 4 actually does mean somewhat light polluted. And so I just wanted to test under some different sky conditions to give you a feel for what these filters do in a more sort of rural setting like Bortle 4, but then we'll also jump into a city setting Bortle 9, which is basically almost as, about as light polluted as you can get. Well, Bortle 4 you can think of as is still a fairly nice night sky. You can make out the Milky Way in the summer and you can make out M31 naked eye. So here's what the North America and Pelican Nebulae looked like without any kind of filter and a stock Canon 5D Mark III. And here's that same scene with an Optalong L-Pro and then a Bader Neodymium Moon and Sky Glow, the Astronomix CLS, and finally the SV Bony CLS. And now let's look at some crops. This is no filter on the Cygnus wall. This is the L-Pro. This is the Bader Neodymium. This is the Astronomix CLS. This is the SV Bony CLS. Okay, next let's look at that same night I shot with a dedicated astronomy camera. A dedicated astronomy camera has no IR cut filter, or this one doesn't have an IR cut filter built in. This is the QHY168C. So instead of going no filter and then comparing the rest, for my baseline image, I used an Astronomix L2 UV IR cut filter. But it still gives you an idea of without light pollution filters added, what to expect from this camera and these sky conditions. So here we go, same scene. It's a little bit cropped in because this is a crop sensor camera while the 5D was full frame. So here is with just the Astronomix L2. Here is with the Optolung L-Pro. Here's with the Bader Neodymium. This is with the Astronomix CLS. And this is with the SV Bony CLS. And now let's look at some crops just to the Cygnus wall. Here's the Astronomix L2. Here's the Optolung L-Pro. This is with the Bader Neodymium. Here's the Astronomix CLS. And finally, the SV Bony CLS. Okay, now I'm sure what a lot of you have been waiting for, let's look at a really light polluted sky. This is from Summerville, Massachusetts, which is portal nine because it's right near Boston, meaning a very, you can, this is an actual picture of the sky, the night that I took these pictures and you can see that you can barely make out any stars. It's just sort of this ugly gray, purple color. And so these pictures are not gonna be as pretty as the ones you just saw because we're under much worse conditions. And the North America and Pelican Nebulae are challenging with a stock DSLR, meaning one that's not been modified under portal nine skies. So this should really show the difference that we get with these light pollution filters. So here is no filter. This is the Optalong L-Pro. This is the Bader Neodymium. This is the Astronomix CLS. And finally, the SV Bony CLS. Let's look at some crops. Here's no filter on the Cygnus wall. This is the L-Pro. This is the Bader. This is the Astronomix CLS. And this is the SV Bony CLS. Okay, and finally to wrap it up, let's look at the portal nine with a dedicated astro camera. Here is with just the Astronomix L-2, the Optalong L-Pro, the Bader Neodymium, the Astronomix CLS, and the SV Bony CLS. And here's some crops. This is with the Astronomix L-2. There's with the Optalong L-Pro, the Bader Neodymium, the Astronomix CLS, and the SV Bony CLS. Okay, to wrap it up, I'm gonna let you make your own judgment about these filters and what might work for you, but just to give you a little bit of what I thought, my feeling was if you do have a dedicated astro camera or a modified DSLR, and you're shooting under dark-ish skies like Bortal IV, then there's really no reason to get a light pollution filter. I thought that the Astronomix L-2, which just cuts off the UV in the IR, but doesn't mess with the rest of the visible spectrum, looked the best out of all of them. My second favorite would be the most gentle of the light pollution filters, which was the Bader Neodymium. My third favorite for, again, a dedicated astro camera or a modified DSLR was the Optalong L-Pro, but it is about $50 more expensive than the Bader Neodymium. And my least favorites were the CLS because they were cutting out a lot of the light so that you ended up with noisier images and with worse star color. So I didn't really see any advantage to using those under dark skies. When it comes to the Bortal IX skies with the dedicated astronomy camera, I thought that they all did a fairly good job and it's really just up to personal preference, but I would probably go with that same order that I said before. I'd stick with just the Astronomix L-2, then the Bader, then the L-Pro, and then the CLS filters. Now, my opinion is pretty different when it comes to the stock DSLR. With the stock DSLR, I found that both from Bortal IV and Bortal IX, all of the filters were an improvement over no filter, but my favorite under Bortal IV was again the Bader Neodymium because it produced excellent star color and just as good a result in my opinion as the other filters in terms of the nebulosity, but under Bortal IX skies, I thought that the CLS filters were probably more what people were going to look for in a light pollution filter and that they really boosted those red nebulae while the Bader did the worst under Bortal IX with a stock DSLR. It basically looked just slightly better than no filter and no filter under Bortal IX was really bad on these nebulae. So if you are under very heavy light pollution with a stock DSLR and you want to get a light pollution filter, I would recommend one of the CLS filters. They come in at slightly different price points. So if you're price sensitive, you could pick one over the other, but really the CLS filters, I thought did best with just a stock DSLR. But once you modify, I think going with either no filter if you do an HA mod or an Astronomic L2 kind of filter, like a UVIR cut filter would be best if you are full spectrum. Okay, so hopefully that was helpful. And remember, you can go to astrophilters.com to see all of these images again and just look at my reviews in bulleted list format rather than as a video. And you can also purchase some of these filters directly from that site through my OPT link or in the description. And again, I'll disclose that I do use OPT's affiliate program. So if you buy one of these filters through my OPT link, I will get a 3% I think, 3% or 4%, something like that commission, but your price won't go up. Okay, this has been Nico Carver. My main website is nebulaphotos.com and thank you very much. I'm glad to have this review off my back, but it's been fun and I hope to do more reviews in the future. Till next time, Clear Skies.