Recently I wrote about making a solar filter for my camera but it’s taken a while to get round to using it. I had a quick go today, using my Canon 450D and a Tokina 400mm f/5.6 lens.
The results are a bit iffy – there were massive problems with internal reflections in the lens tube. The filter itself consists of two plates of glass with a thin layer of nichrome between them. This on its own gives several surfaces for reflection problems.
Common wisdom says that stopping down a lens increases sharpness (to a point) but in this case, the smaller the aperture, the more area there is of the aperture blades to reflect light back up to the mirrored filter. All of the photos have lots of flare, which I was able to reduce somewhat. Perhaps with practice I will learn techniques to work around this.
This first picture is a straightforward picture of the sun. The red “corona” around the bottom-right hand side is actually lens flare.
The second picture is made from the source data as the first picture, but is only showing the green channel in monochrome. It has less flare, since most of the flare was red. It also seems to show off more detail of a band-like structure across the centre of the sun (although this could be down to lens flare, Newton’s rings, or some other kind of defect).
Jonathan Gazeley 