I wanted to see if there're any stains on the sensor of my Canon 5D MK3 and I took this shot of a white surface shaking the camera with a slow shutter speed. I keep getting the same image with such a weird pattern.

Is this just dirt?

ISO 100, f/22, 1/25 sec, 50mm enter image description here


1 Answer 1


It's something on the surface of the cover stack over your sensor. I doubt it's "just dirt" though. Some of it is probably dust that can be blown off easily with an air blower. (Do NOT use "canned air"! It will leave residue behind.) But some of it is probably stuck to the sensor a little bit. It's time to do a wet cleaning of your sensor if you need to take photos at narrow apertures. Wide open with a fast lens those spots probably won't even show up.

The subject of cleaning sensors has been well covered here. For more, please see:

What to do about persistent dust spots on my DSLR?
Why are these black dots / spots appearing in my pictures?
How to clean spit off my camera sensor?
Dust on Sensor After Many Cleanings DSLR

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    \$\begingroup\$ Looks most like dried liquid impurities to me... like someone did a really bad job of a wet cleaning before. \$\endgroup\$ Commented Nov 26, 2021 at 19:29
  • \$\begingroup\$ @StevenKersting Could be. Or oil splatters . Or condensation due to rapid temperature changes when there was already a lot of dust on the cover glass. Or spittle from someone trying to clean the sensor with their moist breath... \$\endgroup\$
    – Michael C
    Commented Nov 27, 2021 at 13:33

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