Hi, Julian!
While the effect on the water is consistent with long exposure photos, the corners went haywire. That can be either from condensed water forming due to the temperature difference at the long exposures, or from the extreme f22 aperture, which can bring overall softness and loss of sharpness. I recommend using a maximum f18 aperture in these cases. And be careful with condensation. It can ruin the lens. Try using a lens cap and for really long exposure photos when temperature shifts radically, put some insulation on the lens. :)
What do you mean with 'the corners went haywire'? Thanks for the tips, I will start testing with them on my next trip. And how do you mean use a lens cap, in what way. I have them on before I use the lens, and I have a filter on every lens for protection
You can see a strong difference between the center of the frame and the corners, in sharpness and overall detail. I don't think it is because of the compression factor when you uploaded it. Or, it was windy? If the wind blew, it can cause branches to move and falsely give the sensation of softness in the top right corner. That and the movement of the clouds over the 3 minutes exposure. Else, the reasons could be the two above mentioned. Cap = Hood - sorry. I meant hood. :) Sometimes it protects the filter / the front of the lens from temperatures shifts creating a buffer. Test a little bit and see what's best for ND usage. The movement can bring chaos into a long exposure photograph, that's why you must consider the time of day, weather forecast, etc.
Aha, yes it was windy. Longexpusure is definitely a different beast to tackle, very interesting though!
So the main problem is shifts in temperature right? Since I will be going to Iceland next month, but I think it will just be cold all the time :P
Very careful with cold. The camera is weather insulated? The lens? If you will love long exposures, and you will, I think you will try to start thinking of portable weather resistant photo gear. And in Iceland, don't just bring the camera and the lens from -10 / -15 to +22 degrees of the home. Just leave it in a neutral zone for some time before getting it into the warmth of the home. :)
Much appreciated all these tips <3 I believe the camera is weather insulated, will double check