Heat Shimmer Blues
Heat shimmer, it can occur over nearly any surface from sand, snow, water, sage, and so much more. The transfer of heat from a surface to the atmosphere is a naturally occurring phenomenon that we normally don’t see or take for granted. When you start shooting with lenses greater than 200mm though, you can start seeing it. When you get to 500mm and greater, it’s an issue you must be aware of if you want sharp images!
Many photographers though don’t recognize it when it’s in the viewfinder. That’s because it’s a moving “gas” that comes and goes with the air. Last week when shooting on the beach, we had no heat shimmer for the vast amount of the time. It wasn’t until near the end that it rose. If you look at the top photo of the Purple Sandpiper taken with the Z6 / 800mm, you can see the eye and legs are sharp. The shot taken at the end of the shoot of the Purple Sandpipers, you can see that those two elements are just not tack sharp. While critically focused on the eye, the heat shimmer creates a curtain of shimmer. When I called it out, some in the group didn’t recognize it at first. But it got so bad that the AF system which was grabbing on to subject readily, would no longer grab focus. So if you have images that you know, you swear were sharp but turn out soft, there is the real possibility it was heat shimmer causing you a focus issue.