ND filters for the Solar Eclipse.

workshops-275 ND filters for the Solar Eclipse.

I know many of my readers are planning on travelling to the US and the path of totality to shoot the solar eclipse on the 21st of August.

A couple of words of caution.

First, make sure you never view the sun directly or through an optical viewing device such as a DSLR camera, telescope or lens without covering the lens with a dedicated solar viewing filter.

DON’T try to use sun glasses, welding goggles or conventional ND filters.

Most regular photo ND filters only cut the visible spectrum. Many will pass IR (Infra Red) without much attenuation. When shooting or looking at the sun it’s not just the brightness but also the IR that can damage your eyes or the sensor as this is where most of the heat energy is. So a 16 stop ND might well reduce the brightness of the sun to a useable level for a video camera but may not reduce the damaging IR and heat. This could lead to damage to the cameras own ND filters or the sensor itself.

To look at the sun with your eye’s you MUST use a proper solar filter or solar viewing glasses. This will normally be a silvered reflective filter or film. The silver reflective coating reflects away the harmful and damaging infra red as well as reducing the brightness. If the filters you are using are of the film type, check for pin holes in the film before using them.

On a video camera it is much safer to use IRND filters rather than conventional ND filters if you can or add a good quality IR cut filter in front of the ND filters.  Don’t skimp on the filters you use.

Make sure you have enough ND for the camera to use an aperture wider than f11. If you are having to stop down to f11 or f16 you will not be getting the sharpest possible image due to diffraction effects. On cameras with smaller sensors such as 2/3″ or 1/2″ you really want to have the aperture more open than f8 for the best results, so that means you’ll typically need 16 stops of ND!!

Try to avoid screw on filters. Once the moon completely covers the sun you will want to quickly remove the heavy ND filters. Then once the sun comes out from behind the moon you will need to replace the filters very quickly. So use something that allows you to do this quickly and easily. A mattebox with slide in filter trays or magnetically attached filters are a good way to do this.

If shooting with a very long lens to get the sun to fill the frame you will be surprised by how fast the sun will move through the frame. So you will need a really good fluid head to allow you to slowly track the sun without jarring or bumping the shot.

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5 thoughts on “ND filters for the Solar Eclipse.”

  1. I’ve ordered a 4 x 4″ filter that “reduces light to 1/100000th or 16 3/5 Stops” to use on my FS7 M2. Is the IR cut an issue with this camera? Now that I read this post, I plan to get my hands on IRND to put in front of this filter, but am wondering if it’s necessary, or perhaps the FS7 M2 already has some IR protection on the sensor?

  2. The FS7’s ND filters have at least some degree of IR reduction as they are effective at controlling the magenta color cast than can sometimes be seen due to IR contamination on other cameras. But the risk is that you rely on the 16 stop ND to reduce the light level but then have IR energy that is at the equivalent of 16 stops higher than the visible light which you are using for your exposure reference. This could lead to damage to the sensor or the cameras built in ND filters. Over the years there have been quite a few examples of shooters that have damaged the FS7’s sensor by shooting the sun so the sensor is definitely not IR or sun burn proof and a non IR cut ND filter makes this much more risky.

  3. I’m also using a solar filter, that is reducing the light transmission by a factor of 100000, put in front of the lens (in fact, a refractor telescope). It’s made by Baader, it’s name is “AstroSolar Safety Film OD 5.0”.

    I have been using this film from Baader several times, for several total solar eclipses. Baader is claiming that “you can use our AstroSolar Safety Film OD 5.0 on large Schmidt-Cassegrain telescopes WITHOUT adding an IR-Cut filter. The AstroSolar Film of course has to be put before the objective lens.”

    See here (comments):
    http://astrosolar.com/en/information/about-astrosolar-solar-film/astrosolar-technical-info/

    Take care anyway! And be sure that this is the film you have effectively bought!

    Jean

    1. Good to hear from you Jean.

      My understanding is that most of the solar film type filters cut IR by reflecting it away, which is part of the reason why films like the Baader AstroSolar have mirror like surfaces. These are the correct type of filters for the job. A traditional photography ND filter is normally an absorption filter and as a result will not reflect away the IR in the same way unless it is an IRND.

      1. Alister, I think that you are perfectly right, as always! Now, you know why I was testing RAW on the FS5…

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