I just took a screenshot off the raw file.
Exposure Time: 10secs
Focal length: 24.0mm
F number: 16.0
Filter: hoya ndx400 ND filter
There seems to be bad purple artifacts and a white shiny line at the bottom of the photo. I can't seem to figure out what's wrong. The line and purple artifacts only appears in long exposure shots. The purple artifacts are sometimes worse in some photos.
What I did: tried to clean the filter using a pen, and removed it, and then put the back the filter. The line still exist in the same position.