PureNight FAQ

Lonely Speck PureNight Light Pollution Reduction Filter

PureNight Frequently Asked Questions

Here are all of the most frequently asked questions for the PureNight Light Pollution Reduction Filter!

Where can I order?

Pure Night is currently only available via crowdfunded pre-order via the Lonely Speck website. Pre-order PureNight here. We have an expected shipping date of March 2017.

What kind of improvements can I expect from the PureNight?

PureNight is made of didymium glass. Didymium filters out sodium light which is typically one of the most prevalent forms of light pollution. Sodium vapor lamps are very commonly used in industrial and street lighting. By removing this yellow color from photos, colors of the night sky tend to be more “true” and less editing is required to compensate for the yellow color of light pollution.


Didymium blocks the transmission of yellow-orange light between about 575nm and 600nm wavelengths, the same wavelength as sodium vapor lamps. In the example above, look at the drastic brightness change around the lights of the town on the bottom of the frame. Below is a preliminary transmission curve based off our prototypes. The final transmission curve of the production units might differ a little bit in magnitude but otherwise should be very similar.


Because PureNight targets specific colors, PureNight is not effective at filtering out white sources of light such as LED lamps. Certain municipalities are adopting brighter and whiter LED lamps that are much more difficult to filter. The only real solution for this type of light pollution is better lighting practices at the source or traveling to darker site.

Balanced Example

The biggest advantage of the PureNight is an increase in contrast. Light pollution reduces contrast by illuminating moisture in the air. Filtering out this light makes the surrounding sky darker. A great example of this improvement can be made be making a comparison between a filtered and non-filtered image and adjusting them in post processing to match in both white balance and exposure.


The difference is subtle but most noticeable especially around the galactic center. If we take a closer, 100% look at the galactic center, we can see that image made with the PureNight retains more of the subtle reds and pinks of the nebulae and shows higher contrast around the galactic center.


The PureNight is expected to have a filter factor of 1.3 to 2 meaning that there will be a reduction in light transmission of the image by about -0.3EV to -1EV. To get a better idea of what to expect, feel free to download our sample photos in RAW DNG here. (95.6MB, .zip)

How does PureNight differ from a Red Intensifier like the Hoya Intensifier?

We love the Hoya Red Intensifier. It’s certainly an affordable didymium filter option that we recommend. Limited availability of the Hoya Intensifier and the lack of a square version led us to pursue the design of the PureNight. We’ll be using didymium glass with similar filtration properties to the Hoya Intensifier. That said,  there are a few shortcomings of the Hoya Intensifier that PureNight aims to improve upon.

For one, PureNight will be available for square filter systems (85mm and 100mm at first). This allows photographers to use a single filter system across their lens collection. Eventually, we hope to add availability of 67mm, 75mm and 150mm sizes to make PureNight the available to nearly any filter system, including those for the ultra wide angle lenses like the Rokinon 14mm f/2.8, Nikon 14-24mm f/2.8 and Tamron 15-30mm f/2.8.

The final and most important improvement: the Hoya Intensifier is made of either uncoated or single coated glass which can be more problematic in flare-inducing conditions (like if there is a bright light source against a dark background).  To improve upon this shortcoming, PureNight will be multi-coated for anti-reflective properties rather than the single coated (or uncoated) Hoya.

Which filter holder do you recommend?

To mount a PureNight you will need:

  • Appropriately Sized Square Filter Holder System
  • System Compatible Sized Adapter Ring for Your Lens Filter Thread Diameter


To determine which size filter holder system (85mm, or 100mm) and which adapter ring you will need, you will need to know your lens’s filter thread diameter. The filter thread diameter is usually marked in millimeters on the front of your lens with a diameter (⌀) symbol like this:


In this example, the lens shown has a filter diameter of 49mm. Depending on your lens’s filter diameter size, we recommend the following systems. In general, pick the system size that’s larger than thread diameter of your lens:

Is PureNight available in 150mm sizes? Will the PureNight fit a fixed hood lens like the Nikon 14-24mm/2.8 or the Rokinon 14mm/2.8? Will other sizes be available? (67mm, 75mm?)

150mm PureNight is not yet available but we’re working on it. We initially wanted to launch on 85mm and 100mm systems because those systems are much more popular. That said, we have received a LOT of questions about making PureNight available for 150mm square filter systems like the  Lee SW150, NiSi and Haida.

Because of the filter’s larger size, we’re still working out some of the finer details like fit, packaging, etc. The 150mm size is a lot of glass. It’s nearly 4x the amount of glass as the 85mm size so with that comes a lot higher manufacturing costs. We also want to be able to offer at a price point we thing reasonable so we’re going through the work to try and make that possible.

Ultra wide angle lenses like the Nikon 14-24mm/2.8 and Rokinon 14mm/2.8 are some of our favorites for landscape astrophotography so we’re hoping to get a 150mm PureNight design sorted out.

When 150mm filters are sorted out, we’ll promptly try to make the 67mm and 75mm sizes available as well.

Do you ship outside the USA?

Yes, we will ship internationally. Please remember that the PureNight is currently on pre-order with expected shipping date of March 2017.

Shipping fees vary for all our international orders. International postage fees for small packages were increased as of January 2016 by the US Postal Service and our current pricing reflects those changes. It’s typically about $15 for packing and shipping to send a PureNight order outside the USA.

Our international orders are shipped via USPS first-class mail and usually take 7-10 business days to arrive. Tracking may or may not be available depending on the destination. As the buyer, you are responsible for any import taxes (VAT, etc.), duties and custom fees that your country may impose at the time of receipt of the shipment. All international shipments are marked on the customs form as “Merchandise” with an accurate description of the value and contents (“Photographic Filter”) and labeled with the proper six digit HS Tariff Code for photographic filters: 900220. Please check with your local postal service for status updates on your order once it has left the USA.

More FAQs coming soon.

For further questions, just ask in the comments below or contact me directly. –Ian Norman

17 Responses

  1. Joseph Aczel January 11, 2017 / 6:24 pm

    What is the advantage of this filter over a dedicated LPR filter like the Kenko Astro LPR?

  2. Chris December 29, 2016 / 2:54 am


    Is the PureNight filter effective for night cityscape photography? I live in a major Asian city and don’t travel much for astrophotography, but I love to take night shots in the city. Will the PureNight give me better shots, or is this primarily for sky?

    Thank you.

  3. Marc December 16, 2016 / 10:58 pm

    Hi Ian,

    Congrats on the product.

    How will the quality if the glass stack up to the B+W Redhancer?

    I was lucky enough to track one down last month.

    • Ian Norman December 17, 2016 / 6:15 pm

      We are likely going to meet or exceed the standards that most B+W photographic filters are built to in terms of optical flatness. Our goal is for the PureNight to be usable on fairly long lenses on it without noticeable image degradation. This is a premium priced product and we want it to perform as such.

  4. James December 16, 2016 / 7:50 pm

    Can you do the same thing with lightroom and photoshop? The effect doesn’t seem to be that great. It almost looks like just WB change + contrast + selective color balance, which I need to do anyway.

    • Ian Norman December 17, 2016 / 6:21 pm

      A portion of what the filter is doing can be emulated with photoshop but the real advantage is the improvement in contrast from each raw frame made with the filter and the resulting retention of color details, especially in nebula when shooting in less-than-ideal conditions. My quick balanced comparison above is what I think is a fair representation of the benefit of the filter when used in a fairly heavily light polluted area (suburban Los Angeles). No doubt, the difference is subtle but tangible and that may or may not be seen as a benefit to certain astrophotographers. I’ve very much enjoyed shooting through this filter and I think it’s a tool that I will continue to use for the foreseeable future.

  5. Ed Coenen December 15, 2016 / 2:58 pm

    Please, can you give examplea of city lights in streets?

    • Ian Norman December 17, 2016 / 6:10 pm

      I am working on some new samples with our coated prototypes for the most accurate representation of the final product. I hope to publish those shortly.

  6. Brian Irwin December 15, 2016 / 12:22 pm

    Hey Ian,

    this looks really cool, so I hope to get one in my grubby little hands. I have a couple of quick questions;

    1, You mention the Rokinon/Samyang 14mm f2.8, do you have a way to mount a filter with those? I thought you had a back-burner project to get around the bulbous front element and lack of filter treads (but I could be thinking of the wrong lens).

    2, Do you have any sample photos using this as more of a ‘walking around’ filter? Long exposure night photos often pickup the Orange colour cast reflecting back from the clouds, so it would be interesting to see that as a comparison. That is easier to fix in LR, but it would be interesting to see if it would make a difference.

    • Ian Norman December 15, 2016 / 2:54 pm

      For the Rokinon 14mm, we will be launching a 150mm version for Lee SW150, NiSi and Haida filter holders. That’s in the works and coming soon for pre-order. We’re still working out the final details.

      I tend to leave mine on for night photography. It now lives in my holder. Where it might be unsuitable is if you think the 0.3 to 1.0EV reduction in light is detrimental to the ground in the photo. If the ground illumination is by scatter of light pollution, the filter will basically make it black. This is where a simple exposure composite can be very helpful. A stack of shots with the PureNight for the sky and a few longer exposures stacked without the PureNight for the foreground.

    • Brian Irwin December 16, 2016 / 9:16 pm


      Thanks for getting back so fast, and congratulations on funding the 100mm. Hopefully you can get them out ontime (or a few weeks early) as am planning to head out to monument Valley around March 27th in hopes of getting my first proper galactic center.

      1, Thank for the info re: the Lee SW150 etc., I didn’t realize they were out. That got me googling again and I found the cheap mans option and ordered a Samyang SFH-14 Filter Holder on ebay. At $30 I am not expecting perfection, but I don’t think the 150mm would work on my timeline. So i will fallback to the 35mm f1.4 🙂

      2, You make a very good point re: the reflected light off the ground, luckily a lot of what I shoot at night is memorials and stuff (living in DC) so they have dedicated light, but it will be fun playing with the filter to see what light we are really getting.

      Would love to see some of your examples from Street level, with so many different types of street lighting in use today I imagine the lighting is complex.

  7. Grant Johnson December 14, 2016 / 10:28 pm

    Assuming this is the case, but I’d love to be wrong… Is this lens susceptible to interference fringes – those irritating concentric circle distortions – when photographing aurora?

    • Ian Norman December 15, 2016 / 1:27 am

      That’s a really good question and one that I’m not ready to answer. I’ll try my best to do some testing on the PureNight with aurora before its final ship date to give you a better answer. (winter Alaska trip anyone?)

      Do you have any resources where I can read about the root cause of the interference fringes? If it’s just due to monochromatic light passing through two bonded surfaces as with some filter constructions, the PureNight should not have the problem as it will be made from homogeneous glass. That said, I’m not totally familiar with the phenomenon so maybe that doesn’t matter.

    • Grant Johnson December 15, 2016 / 1:49 pm

      Here’s a good image showing what the interference fringes (also called Newton’s Rings) end up looking like: http://www.ptialaska.net/~hutch/Rings.jpg

      From what little I can understand of the phenomena, it has to do with the narrow wavelength of the aurora’s spectrum diffracting back & forth off of the parallel faces of the filter, causing a standing wave which leads to the ripple pattern.

      I’ve seen discussions about it on http://www.alaskaphotographics.com/blog/how-to-photograph-the-northern-lights-with-a-digital-camera/ and http://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/313492-weird-circular-rings-night-photos.html. Other sites go into the mathematics and physics of the optics, but that’s far above my head.

    • Ian Norman December 15, 2016 / 2:50 pm

      Well I see if I can get a chance to test it up north this winter!

  8. Brendon December 14, 2016 / 8:05 pm

    How does the filter go with IR modded cameras like the 5Ds R or cameras that have had the IR filter removed for Astro photography? Does it cause a reduction in the Ha spectrum access to which is why the IR filter is removed?

    • Ian Norman December 15, 2016 / 1:33 am

      Hydrogen Alpha is about 656nm which is not absorbed by didymium glass so the filter should work for Hydrogen Alpha imaging.

Leave a Reply

Your email address will not be published. Required fields are marked *