Waddencoast photography weekend

Today is the first day of the Groningen Wadden coast photography weekend. It's a great group and I've already been able to teach them quite a few things. When the day was over with, I made a couple of images in the harbor near the hotel where everyone is staying.

Can you see a horizontal green band in this image? This has happened to me before, August last year. At the time, I thought I had a filter on that was probably not placed correctly, but now I'm certain I didn't use any filters. I don't like this at all. The Canon EOS 5D mark IV is a very expensive camera and I'd think it should not produce these effects. After some searching on the internet, I found this page that seems to describe the same problem and how Canon fixed it. I'm going to write to the store where I bought the camera. It has a 5 year warranty so maybe they can so something for me...