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.

PureNight is Out of Stock. Can you notify me when it’s available?

Yes we can! Enter your email here:

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

31 Responses

  1. John Morgan August 18, 2017 / 3:03 pm

    Your filter is made of didymium glass, which is homogeneous and not interference based. I understand it will filter light the same no matter whether it comes straight into the lens or on extreme side angles such as with an ultra wide angle lens. Are all the other (competing) filters interference based, which would have severe trouble working as intended with extreme side angle light into ultra wide lenses which lengthens the interference spacing and change the filtered frequencies? And wouldn’t having extreme side angle light into an interference filter cause it to be smeared linearly across the sensor from the light bouncing back and forth different number of times (1 or 2 or 3… etc) before entering the camera? If so, that problem would be eliminated with your homogeneous filter with non-reflective coatings, correct?

  2. Leanne July 22, 2017 / 12:13 am

    Hi Ian, I have one of the light pollution filters, I’m from New Zealand so our light pollution is somewhat limited from the US, can you recommend a white balance to use please? I have noticed that on your examples it is set at daylight is that a recommended practice with the pure night filter?

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