Solar filter for Canon EF 100-400mm F4.5-5.6L IS USM (Mk I) lens.

Solar filter for the Canon EF 100-400mm F4.5-5.6L IS USM (Mk I) lens.

This solar filter fits snugly on the end of the lens. You will need the actual solar film to construct this as the 3D printed parts are only the frame. You can buy this on Amazon or any telescope supply company. I like both Thousand Oaks Optical “SolarLite” film, which gives a yellowish cast to the sun, and Baader AstroSolar ND5.0 Visual solar film, which gives a more natural white (slight bluish) cast to the sun. A 4"x4" sheet is large enough as the actual film is cut to a 84mm diameter. Use the cutting template and razor knife to cut the film.

This lens is a bit different as it has a tapered objective end, so I designed this cap to fit with room for a standard screw filter installed, like a UV filter used for protection of the objective lens. It works with this filter or without and fits snugly over the rubber on the zoom barrel.

This is a threaded design the the solar film is held in place by pinching it in between the body and cap. They are threaded with a ultra-fine M85x1 thread.  This thread can be frustrating with 3D printed parts, but some patience is useful. Use a 0.4mm nozzle and very fine layer height for the threaded feature (0.07mm - 0.10mm layer height). Use variable layer height for the body as the rest of the body can be made with 0.30mm layer height. I like PLA+ for these and have had better luck with PLA+ than PETG for fine threads like this.  I've added a loose fit cap that can be useful to at least getting the threads started on the body. Work the threads in by twisting back and forth and then cleaning any plastic debris/dust and the then the threads should be relatively smooth. Finally, assemble the filter with the film.