From the FAQ: "Q. This changes too fast, it always shocks me. A. The f.lux transition can be CPU intensive, so f.lux tries to be polite about it. To make it slo

From the FAQ: "Q. This changes too fast, it always shocks me. A. The f.lux transition can be CPU intensive, so f.lux tries to be polite about it. To make it slow, you can use the special 1-hour slow transition option under settings instead." That's a nice option to turn on.