On August 21st of this year there will be a full solar eclipse passing over the central United States, with the center line cutting through southern Illinois. Since this will only be a few hours south of me, I will be driving down and photographing the event. The last one I can recall was in the early 90's and I was in middle school, so I am quite looking forward to seeing this.
You can't shoot the sun without heavy filters on your camera so I ordered a black polymer filter sheet from Thousand Oaks Optical to use with my 600-1000mm lens. A lot of sites recommend you just rubber band the sheet over the end of the lens but I wanted a nicer (and re-useable) solution than that. I have a 100mm square filter holder for my regular ND filters, so I decided to put together some kind of insert for the sheet to slip inside my holder.
My ND filters are 100mm squares and only 1 or 2mm thick, so the challenge is to make something rigid enough to 'frame' the solar filter yet thin enough to slip into the holder. I poked around with a few different kinds of cardboard but everything was too thick or too flimsy until while getting breakfast the other day I grabbed a box of Cheerios and realized the cardboard was absolutely perfect. Rigid and thin, I could cut two pieces out and using an exacto knife cut a window for the filter.
The edges didn't have to be perfect since they were outside the field of view plus this will probably be proof of concept until I can find a better material. I cut down the solar filter sheet and taped it into the frame, then taped the two frames together.
The sheet is delicate and even though I was careful I somehow scratched the front of it. Not a big deal, the sheet itself was only a few bucks. I put everything together and mounted it in the filter holder attached to my lens making sure the silver side is facing the sun.
The solar filter is so dark that the sun is the only thing you can see when its mounted so getting the camera aligned with the sun and focused is a bit of a trick without burning out my left eye. I found that when I squint while shooting with my right eye behind the camera my left eye is still kind of open, enough to where if I am pointing at the sun its very uncomfortable. I slid my hat down over my left eye and kept the right behind the camera so I was safe. Focusing was tricky, but I got dialed in and started making exposures. To my surprise I had to bump my ISO to 800 while shooting 1/250th of a second but I figure I can probably drop my shutter speed a bit when it's on the tripod. I will probably grab a blanket or some kind of hood on my next test run so I can use live view to get even sharper focus.
Next up is to search for a better material to use as a filter frame, however if I don't find anything I know that using this simple method works just fine. I'd also like to try using a hood over the tripod so I can focus better without getting blinded in the process. Remember you have to be very careful while viewing or photographing the sun, as even a second or so of direct contact can damage your eyes or equipment. I'll post some more updates as I make progress.