Do you know that your camera in normal use is good only for about 75,000 clicks? Do you want to increase that number way beyond? On close examination of the images, do you see shaded spot/spots? It's time to clean the sensor. Clean once every 3 months, whether the camera is being used or not. Clean the frame sensor and the lens. Although we know the operations for most cameras to keep the mirror open to expose the sensor, we advice you to bring the camera manual along. Cleaning lens and frame sensor takes about 30 - 40 minutes.