[frank]

Recently I got some dust-like spots on my images when I shot sky. An example is shown in the image below. I switched lenses but they stay there. I thought they were caused by some dust on the image sensor so I cleaned the sensor by blowing it with air. I then checked the image sensor, it looks clean and had no dust on it. But I still get the dust-like spot. Can somebody tell me what it really is and how can I get it off?



Many thanks,

Frank