I'm quite new to long exposure and it is a technique I want to become better as an amateur landscape photographer, but I'm having a little bit of banding in one of the top corner of the sky in my photo. I'm probably at fault, but I don't know what I did wrong. It was a cloudy evening, the banding is the same color as the clouds, it is not a colorful banding. It is not major, but it is annoying. I used a D610 with Samyang 14mm and a Fotodiox ND16 (RAW, f/8, 200sec, iso 100, long exposure NR On). I've shot some 30sec exposure photos before with this setup, but it was the first time the exposure was that long.
I know it would be much better with the example, but I tried to upload the photo on Flickr to show you what I'm talking about, but it is just so slow, I can't upload anything anymore. At the first sight of the settings I used, is there anything wrong?