The camera was mounted at the rear end fixed with the two fin screws by a bar. The lens fixed 1cm under the planing water level (to avoid view of all the airbubble under the board running through) adjusted to look to the fin tip which a have coverd with a orange self addhesive film for better view. By this setup you can not see the full fin length up to the basis, app. 60% of the length.
To GEM: The main flex of my F1 fin (and all other brands) is beginning from the basis up to app. 50cm of length. The tip (last 20cm) will not flex to much because of relative less forces in this section. Dont forget, the bending force is caused by the uniformly distributed waterload. So at the tip end no load and than the load is permanent increasing up to the basis. I found the sum of all water forces on my fin is only a little smaller than my body weight. However it is difficult to make the fin in the tip so soft to have in this section some remarkable twist. Difficult because there will be not to much reinforcment in there anymore and if you tough the ground or catch a fish the tip will easily brake.
To Ion: You are right, the camera is mounted solid. My F1 fin in H+ is compareable to a R19 S! My F1 S is flexing up to 30cm one side! I think except the starting and pumping movement the fin is moreless not moving left/right in the water. So the left/right movement you see on the video is caused by the longitudinal walking of the board.
I will look for some Photos showing the arrangement and will do a short photo video and place it in Youtube. Will be anounced!