This Slide-In Filter Cuts Light Pollution in Canon and Nikon DSLRs

The Taiwanese company STC Optical has created a slide-in filter for Canon and Nikon full frame DSLRs that can reduce light pollution in astrophotography. It’s called the STC Astro-Multispectra Clip Filter.


The filter is installed in Canon and Nikon DSLRs by sliding the filter into the mirror box after locking the mirror up in your camera’s settings. After mounting your lens, the filter will sit firmly in place between your sensor and your lens.


Once installed, the filter helps to reduce the wavelengths associated with artificial city lighting while enhancing the wavelengths found in photos of stars (e.g. Hα, Hβ, OIII and SII).

Since the filter requires the mirror to be locked up, you’ll need to use Live View to frame your shots, as your optical viewfinder will be blacked out.

Here are some example photos taken without (left) and with (right) the STC Astro-Multispectra Clip Filter:






The STC Astro-Multispectra Clip Filter is available now for Canon and Nikon full frame DSLRs from the Hong Kong store Cyclops Optics for HK$1,620, or about $208.

Last week we featured a similar product called the PureNight filter. Instead of sitting inside the mirror box of a DSLR, however, the PureNight filter is mounted to the front of your lens.


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  1. Reply NJOceanView December 23, 2016 at 10:43 am

    I’m assuming this would be installed in a very sterile environment, as sensor dust could both get in and then be trapped by the filter.

  2. Reply SiriusPhotog December 23, 2016 at 10:43 am

    I don’t see this doing much unless the IR filter in front of the sensor is removed. AKA astro-modded. These results shown here can be achieved with Lightroom.

    • Reply TerryPA December 23, 2016 at 10:43 am

      Since the filter cuts out light non-uniformly in the yellow range (which the sensor picks up as red and green). I don’t think it can be replicated truly in Lightroom (in the same way you can’t truly replicate a circular polarizer)

  3. Reply karmazen December 23, 2016 at 10:43 am

    This should shift infinity a bit, I had a AA filter for the 5DII to shoot cleaner video, same system but it did mess with infinity and any close to parfocal lens would really be a mess if you focussed and zoomed out.

    Results look impressive.

    • Reply Zos Xavius December 23, 2016 at 10:43 am

      ok so you had a 5dii. i’m curious how you kept the mirror up all the time for the filter? did you just drop into live view, place the filter, and then attach a lens?

      • Reply karmazen December 23, 2016 at 10:43 am

        Yes that is all and when you turn the camera off the mirror just dropped on the filter.

        • Zos Xavius December 23, 2016 at 10:43 am

          Ok thanks. Yeah I don’t see how the mirror falling on the filter would actually hurt it so I guess it would be ok.

      • Reply Arlington Brian December 23, 2016 at 10:43 am

        @zos most cameras have a mode you use to clean your sensor that will flip the mirror up and hold it up. When you use a blower on your sensor you don’t want live view timingbout and slamming down on nozzle.

  4. Reply dslrforever December 23, 2016 at 10:43 am

    yikes…seems like a really easy way to void your warranty and be on the hook for a new shutter.

    • Reply karmazen December 23, 2016 at 10:43 am

      Why? Locking the mirror is nothing special.

      • Reply Zos Xavius December 23, 2016 at 10:43 am

        some cameras don’t lock the mirror forever. my k-3 does not. if you trigger live view it will cycle the mirror if you dive into the menu for instance. some of the shooting modes cycle the mirror too. if the battery dies the mirror is coming down on most cameras. i know nikons have a decent mirror lockup mode on their better cameras because they have a few lenses requiring mirror lockup. I use an old canon 5dmk2 pretty regularly and I don’t think there is any way to force the mirror up for a long period of time. if the camera times out it just turns off and releases the mirror. i generally don’t change lenses on that camera, but I think you should probably turn the camera off when doing so on ef mount. It might cycle the mirror down if you are in live view and pull the lens off. I’d have to test that.

      • Reply dslrforever December 23, 2016 at 10:43 am

        Yeah nothing special if your lens is already mounted and you’re waiting for the vibration to go down. If you make a mistake and accidentally turn off your camera, hit the shutter twice, or do something else that will accidentally close the mirror on top of that thing, very bad things are going to happen. Maybe your camera has a mirror lock that stays locked without ever resetting itself, I don’t know, but it still takes a lot of trust in a cheap piece of plastic that doesn’t say Nikon or Canon on it.

        • karmazen December 23, 2016 at 10:43 am

          Nothing happens when the mirror drops, the mirror on all SLRs is lever driven up but sprung return, so holding it up is just pushing against the spring, the same way as the lever pushes against it on a long exposure.

          These type of filters have been around for years, if it would damage anything the interwebz would be full of posts about it.

  5. Reply Alan Klughammer December 23, 2016 at 10:43 am

    why would this be better than a filter that attaches on the front of the lens? I guess if you were using a telescope….

    • Reply gameshoes December 23, 2016 at 10:43 am

      I agree with being able to use it with any lens setup, and the cost.

    • Reply Bernie December 23, 2016 at 10:43 am

      Samyang 14mm. Great astro lens. But try putting a filter over it.

    • Reply JC December 23, 2016 at 10:43 am

      Because you can attach any kind of lens instead?

    • Reply Grive December 23, 2016 at 10:43 am

      That’s what I was wondering . Petapixel recently featured one of those.

      Cost would be an obvious answer (since there’s so much less material used…) but this thing costs almost as much as the 85mm front filter…

  6. Reply bunnysoup December 23, 2016 at 10:43 am

    Svett MenneskeYou’d get the same effect with film (or your eyes for that matter). Light pollution rejection filters have been commonly available for astronomy for a couple of decades at least. One thing to notice with these filters is that they dim stars and galaxies along with the sky background, but don’t dim nebulae much because they pass nearly all the light in a few narrow bands that they emit. Still, the resulting contrast is higher all around so the tradeoff is OK. LPR filters for visual use generally don’t filter out the light pollution and starlight as much as photo-balanced LPR filters.

  7. Reply Svett Menneske December 23, 2016 at 10:43 am

    Pretty impressive results. Wonder how it would do with film.

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