If I was a betting man, I'd lay my money on mirrorless cameras being more susceptible to sensor dust ... The sensor is just there, waiting for whatever wants to jump / fall into the body when the lens is off. I struggled with an afternoon of cleaning spots yesterday in images from a Sony a7II. For whatever reason, Sony makes the shake process a manual action rather than auto when the camera is turned off or on, where I'd prefer auto for both.

I feared I'd have to get to a wet clean where I don't have full-sized wipes. I started with a sensor in this situation:



For the long pieces rather than circular spots, I could see these on the sensor with good light and a magnifying glass.

My first tool was a Giotto Rocket-Air and running the camera's sensor clean a few times.



The strips are gone. Maybe hair? I don't know what they are. The next tool is a Sensor Brush. It would seem this could add more than it removes. I blew the brush vigorously with the Rocket-Air, both to remove any dust in the brush as well as to build a static charge before touching the sensor.

Much improved, lots of spots gone, some new stuff arrived.



Another round of brushing and blowing and cleaning cycle and the final result after 20-minutes effort:



Good enough to get out and shoot and better, it seems, than the entire time I've had this body since purchasing used. Most of the images were f/16 at the nearest wall to my computer so I could click the SD card out quickly back n forth between the camera and computer / monitor.

If I was a betting man, I'd lay my money on mirrorless cameras being more susceptible to sensor dust ... The sensor is just there, waiting for whatever wants to jump / fall into the body when the lens is off. I struggled with an afternoon of cleaning spots yesterday in images from a Sony a7II. For whatever reason, Sony makes the shake process a manual action rather than auto when the camera is turned off or on, where I'd prefer auto for both.

I feared I'd have to get to a wet clean where I don't have full-sized wipes. I started with a sensor in this situation:



For the long pieces rather than circular spots, I could see these on the sensor with good light and a magnifying glass.

My first tool was a Giotto Rocket-Air and running the camera's sensor clean a few times.



The strips are gone. Maybe hair? I don't know what they are. The next tool is a Sensor Brush. It would seem this could add more than it removes. I blew the brush vigorously with the Rocket-Air, both to remove any dust in the brush as well as to build a static charge before touching the sensor.

Much improved, lots of spots gone, some new stuff arrived.



Another round of brushing and blowing and cleaning cycle and the final result after 20-minutes effort:



Good enough to get out and shoot and better, it seems, than the entire time I've had this body since purchasing used. Most of the images were f/16 at the nearest wall to my computer so I could click the SD card out quickly back n forth between the camera and computer / monitor.

I had already done a test shot when I read this. I breathed on the sensor glass and wiped smoothly with a never-touched piece of soft microfiber cloth, blowing away any new bits, and then photographed plain paper. This is when I found that my computer screen was also full of spots, so I cleaned that with a different soft cloth. I examined the photo of the paper and it had some spots. I repeated the process and found no spots even many times zoomed in PS. However, I had not read your advice of f16--don't know what the auto setting gave me. I imagine this is a good time to try f32 again, in case spots were just out of focus range.

This adds another whole issue about large and small apertures--I would not assume larger apertures will soften the affect of sensor dust in general photography, and smaller apertures will light them up? After all, my streptocarpus shot (with all the sensor dust) was at f32. My assumption is that the lens f-stop does not affect the focus of sensor dust spots, as they are nearly contact-printed on the sensor (not through the lens). If that is true, the sensor dust will always be in focus (to the degree allowed by the thickness of the glass) no matter what the lens is set on?