Hi guys,


Unfortunately I do not have another lens to test. This is my kit lens, 18-200mm f3.5-5.6 IS, on my 50D.


I need to find a bright torchlight to check the lens.


Just curious since I only have 1 lens, and my lens is always mounted to my 50D. I never change lens. I wonder how and why my sensor will become dirty? Actually when i look at the sensor, I can see some white spots, like dirt on it. But I could not blow it away with my Giottos blower. I feel strange that the sensor are dirty without remove/change the lens. Is this something that could happen?