Schneider 77mm True-Cut 750 IR Filter – Blocks 50% of IR at 750nm. SLR Magic 77mm Image Enhancer Filter – Removes both UV and IR light with a filter factor of 1x.ī+W 77mm UV/IR Cut MRC 486M Filter – Removes both UV and IR with a filter factor of 1x. Tiffen 77mm T1/2 IR Filter – This filter blocks near-infrared (IR)from 680-800nm. Heliopan 77mm UV Filter – A high-quality ultraviolet filter chosen as a “semi-control.” It has a filter factor of 1. I’ve sorted the filters based on the design types. These designs aren’t traditionally considered “light pollution filters” so there doesn’t seem to be any reason to include them. I’m not sure about the inclusion of ultraviolet (UV) or infrared (IR) filters in this test. As mentioned above, some are sized so they fit inside a camera body right in front of the sensor while some thread into a telescope eyepiece.įor this test, Todd limited the filters to ones useful for most landscape and Milky Way photographers – over-the-lens filters. Light pollution filters are available in several form factors. Now that we’ve covered the basics of light pollution filters let’s look at the ones used in the B&H comparison. They are, however, often available as clip-on filters for certain digital cameras where the filter fits right over the camera sensor. In addition, they typically come only in 1.25″ and 2″ diameters for use with telescope eyepieces and astronomy cameras. Unfortunately none of them are very useful for the Milky Way photographer. Some of them are thin-film interference filters. Several types of light pollution filters are available for telescope users. That means a didymium filter will make most stars appear dimmer. The other bad news for didymium glass is that stars contain yellow light. LED, metal halide, and HPS lighting to a lesser extent, contain a number of other colors that didymium does not remove so it has little effect on these lights. However, didymium glass is not a perfect solution for removing light pollution. Didymium Glass – Not a Perfect SolutionĪ large number of light pollution filters are based on didymium glass formulations. In recent years, didymium filters have been used by Nightscaper and Milky Way photographers, removing the amber light produced by both LPS and HPS lighting. ![]() These yellow lines match well with the filtering properties of didymium glass. Low-Pressure Sodium lamps have two bright yellow lines, so close to each other they often look like one line in spectrums. It’s a popular filter for fall colors, as it makes autumn leaves appear more vibrant. By filtering out yellow light (and some green as well), it saturates the red and some blue tones in a photograph. Didymium Glassĭidymium glass has been used since at least the 1970s in landscape photography as a “color enhancing” filter. These filters are glass and either contain chemical elements that absorb various wavelengths of light or have dozens of thin coatings on them that remove the light pollution. To combat this issue, they designed light pollution filters. Filtering Light PollutionĪstronomers since before the turn of the twentieth century recognized that light pollution causes problems observing the night sky. Information on Stopping Light Pollutionįor more information on light pollution, check out my article on what you can do to Save Our Night Skies from Light Pollution. Because of all the advantages over other outdoor lighting options, LEDs are becoming the de facto light for all outdoor uses. Light Emitting Diodes (LED) lights produce the entire spectrum of visible colors at much greater energy efficiency than any other commercial light source. Source: Lamiot, “Leds sodium spectrum“, Licenses You can see the colors produced by the LED are more abundant and will be harder to filter than the HPS. ![]() The higher the peak, the more light is produced for each color. ![]() The output of a High-Pressure Sodium lighting compared with a LED lamp.
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