A Homemade Solar Filter

The sun, photographed with my Nikon D500 and 200-500mm VR Nikkor lens.

I’m not a total die-hard when it comes to solar photography, but I’m going to be close enough to the 2017 solar eclipse event that I figured I’d at least try to get some photos. But first, I had to construct a solar filter. Here’s how I made mine for about $45.

First, decide on which lens you want to use for photographing the sun. I chose my Nikon 200-500 f/5.6 VR lens, because it’s versatile and I can shoot it hand-held if I want to. I also chose this lens because it has a front filter thread, which will allow me to easily mount the solar filter to it.

Materials
Materials for constructing a solar filter: Solar film, step-up filter ring, compass, ruler, marker, paper, scissors, & rubber cement.
  • Solar film (critical): This is the most important material. Using anything other than solar film for your filter can damage your eyes and your gear. I got a 12×12″ piece of solar film from Thousand Oaks Optical for $25.
  • Step-up Ring: This is the frame for your filter. Choose one that steps up to a8-10mm larger filter size so that you have a solid rim to attach your solar film to. Since my 20-500mm lens uses a 95mm front filter, I got a 95-105mm step ring from B&H Photo.
    Note: You cannot use a drop-in filter (on long telephoto lenses) to construct a solar filter. The filter must cover the FRONT ELEMENT of your lens. 

    A step-up ring will attach your solar filter to the camera lens. Make sure your ring has at least an 8-10mm flange on the large (outward facing) side.
  • Millimeter Ruler
  • Drafting compass: For measuring and drawing circles
  • Plain paper: For creating a template
  • Scissors
  • Fine-point permanent marker
  • Rubber cement 
  • Pencil with an eraser
Constructing Your Solar Filter
  • Use the compass to measure the internal diameter of the outside (larger) face of the step-up ring. It’s probably about 1-2 millimeters smaller than the listed filter diameter. In the case of the ring I got, it measured 104mm.
  • Divide the filter diameter by two to get the radius. Use the ruler to set your compass to this length.
  • Use the compass to draw a circle on the piece of paper, then cut out the circle. Do NOT use the compass on your solar film; you will damage it!
  • Check the paper template to make sure that it fits inside the outer rim of the step-up ring without pinching or bunching. If the fit is too tight, make a smaller circle with your compass and cut out a smaller template.

    Check your template by placing it inside the step-up ring. It should fit without binding.
  • Once you’ve confirmed the size of your template, use it to trace an outline on the silver side of the solar film with the fine-point marker.
  • Cut out the circle from the sheet of solar film using scissors.
  • Apply a thin layer of rubber cement to the outer flat surface of the step-up ring. Be careful not to get any rubber cement in the lower filter threads (the small side).
  • Carefully place the circular piece of solar film onto the step-up ring. The silver (reflective) side should be face-up. This is the side that will face the sun. Use the pencil eraser to gently press the edges down into the rubber cement.
  • Remove any excess rubber cement from the filter, being careful not to tear or damage the solar film.
My completed solar filter, with the reflective side facing out.

Once the rubber cement is dry, you’re ready to test your filter. First, hold it up to the sun in front of your face. There should be no sunlight leaks from the edges of the filter. If there are, you’ll need to re-glue your solar film.

Camera Settings

I did a quick test hand-held with my Nikon D500 and 200-500mm f/5.6 AFS VR Nikkor lens. I used the following settings:

1/250s f/8 ISO 560 (Auto ISO) in Highlight-priority metering mode., VR ON

You could also use spot-metering, provided you’re able to hold the camera steady. For the actual eclipse, I’ll use a tripod.

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