Review NiSi ND Filter 20 Stop ND1000K “Black Hole”

NiSi 20 stop ND1000K Black Hole

I’ve used ND filters for many years now, about one year ago I’ve starting switching to NiSi Filters, starting with the V5 Holder and then ND and GND filters. What really convinced me was the high quality standards in every product they made. With the use of proper Schott optical glass the quality is guaranteed, this is the same type of glass used in really high quality lenses, such as Zeiss. NiSi also uses the best coatings: IR to stop infrared light (bye bye magenta cast!), Nano Coating and anti-reflections coating. The new NiSi ND1000K 20 Stop also have all this features, let’s find out how it performs.

A ND1000K (one million)

That’s not a typo, this filter really is a 20 stops, this means a light absorption that will allow you to expose 1.000.000 times longer than a shot without the filter. The filter is a slot-in, with standard dimensions 100x100mm and 2mm thick. It’s compatible with Lee system, tested by me, and of course with the NiSi V5. A gasket is included to avoid light leaking, unfortunately some manufacturers, like Hitech, have decided to include a gasket on the holder itself, making all the filters with a foam glued not compatible. I really can’t understand why, the gasket on the filter is working fine and with this choice they created an holder non compatible with most of the ND filters on the market; fortunately their holder is behind the competition by far. I have quite an experience with 10 stop filters, I own at least 5 brands and I find the NiSi ND1000 brilliant, far superior than the competitors, same for the 15 stops, but I would have never imagined to test a 20 stop. At first I was quite shocked but then I realised that experimentation is the foundation of photography, and this filter is all about experimentation.

NiSi Black Hole 20 stops ND1000K – Optical Quality and Coating

I’ve already written a lot about NiSi Filters quality, and I’m still not tired to say that is great. Like every filter they made, the Black Hole is a full Schott optical glass with superior coatings. The IR coating is really important in a ND so strong, it stops really well the infrared light, even a really small amount can ruin your shots with such long exposures. The nano coating is really handy, cleaning a filter has never been so easy, on the field this is really important and I also had filters really difficult to clean from sea water or grease (like the grease from your hands). With NiSi filters I never had problems with cleaning, grease and water just bounce and don’t stick. The gasket is critical in a 20 stop filter, the Black Hole has a really good foam gasket and I didn’t have any light leaking during my tests.

Tip: Be aware that the gasket is not symmetric, as you can see from the picture below, so you should always insert it in the way shown below, with the edges free from the foam on the right an left side. If you don’t do so the gasket will get stressed and because of the Nano Coating the glue cannot hold as strong as in not-coated filters. Some attention when you slide the filter in will avoid any problem.

Filtro ND NiSi 20 stop black hole

A 20 stops filter, or less?

I’ve tested the real light absorption of every ND filter I had, and not even one was spot on, it’s just the normal tolerance of the production process. The closest one was a ND64 NiSi Filters a couple of years ago, it was about 5.5 stops, so about 8% less than advertised. Some of the worst filters were even 15 or 20% more or less from what advertised. I’ve tested the NiSi 20 stop at 2PM, I took a control shot at 1/165 of a second and I did the math for a 20 stops light absorption.

This is the calculation: 1 / 165 = 0.006 second * 1 million (ND1000k) = 6060 seconds

Yes, six thousands and sixty seconds, about 1 hour and 40 minutes. That’s a bit too much, i really would like to try a 1 hour exposure one day, but not today, and not nearly 2 hours. Then I remembered the error I always found in ND filters, even the best ND was about 8% less than advertised, maybe this filter is not a real 20 stops. I decided to give a try to this theory and I’ve supposed that the filter is actually 10% less than 20 stops, about 18. This means about 1500 seconds, 30 minutes. I decided to slightly increase the ISO and take a 1300″ (21 minutes) photo. That’s the result, before and after.

NiSi 20 stops Black Hole Color Cast

I didn’t correct any colour cast from the photo above, I’ve only applied the lens correction to both (Nikon 20mm f/1.8 – review). The most important test for a ND filter, and even more if 20 stops, is the color cast: I have to admit I was surprised. The color cast is really really low, even less than some 6 stop in the market. I think there is a slightly warm cast, a bit difficult to quantify because of the light variation during a 21 minutes exposure.

Real world use of NiSi 20 stop ND filter “Black Hole”

I had the opportunity to test this filter during my last trip in the Outer Hebrides, so what’s the real world use of it? After figuring out that the NiSi ND filter actually is a 17.5/18 stops the use on the field has increased a lot. With a GND and a polariser the exposure time is long, but not too long (less than 1 hour). The possibilities are really a lot, the photographer creativity plays a really big role here. In only a couple of weeks I’ve found these opportunities using the NiSi “Black Hole”:

  • long exposure with really strong light and brightness
  • really long exposures (half hour and more) to get really uncommon architectural and landscape shots
  • taking photographs with fast aperture (f/1.4, f/1.8) and still take long exposure photography. Is really interesting playing with the deep of field in long exposure photography

NiSi 20 stop ND1000K Black Hole


In this example shot I’ve used the NiSi V5 holder with the polariser, a GND hard 3 stops and f/1.8 with a Nikkor 20mm f/1.8. Thanks to the NiSi ND1000K 20 stops the exposure was 21 minutes, about 2 hours before the sunset. It will be a great addition to my filters bag. If you like architectural and landscape photography this is a must have. The filter is directly sold by NiSi Filter on Amazon, with shipping costs and case included.


Thanks to NiSi Filters to give me the opportunity to test the filter for a month before the release.