I don’t generally get too excited about the mechanics of photographing these days, I’m far more interested in the content of the images. The mechanics of this image actually are a bit interesting, though. If you have some photography knowledge, you may know that the blurring of the clouds in the sky is due to a long exposure. In this case, without looking at the metadata, my guess is the shutter speed was on the order of 15 seconds to two minutes. Even at the 15-second low end of that range, though, turning blades of a windmill typically would move so fast as to have registered in the image much like the blades of a propeller airplane engine. Why do the blades appear so still?
Well, obviously, because they weren’t turning. This windmill field was newly installed when I photographed it, and probably had not been brought online yet. Importantly, the blades of the windmills were stopped from turning. But not perfectly so — they were permitted to move very slowly, my guess being that truly stopped windmill blades would undergo an extraordinarily high amount of stress in a stiff wind, and so even stopped windmill blades must be provided a bit of slack to turn. That is why the blades of the windmill in the foreground appear slightly ghosted. The blades oscillated back and forth between the positions over the course of the exposure.
As mentioned, I generally don’t get too excited about photography mechanics, and these days am more focused on image content. Seeing these gigantic windmills up close in the rolling high plains landscape west of Cheyenne, Wyoming was a surreal experience, and the blurred clouds and ghosted windmill blades help evoke that feeling, I think. Still, the mechanics of the image in this case are kind of interesting too. More practically, it’s unlikely I’ll be able to get another photograph like this one, because the field has become active and the blades now turn with a fair amount of speed. Any exposure time sufficient to create blurring in the clouds now most likely would indeed cause the windmill blades to look like the blades of a propeller airplane engine.