One of the things I don’t like about the Sony (perhaps the only thing?) is that it seems to attract dust on the sensor. I try very hard to avoid dust – putting the lenses face down on a hard surface and keeping the camera body facing down as I unscrew one lens and move across to the new one – but somehow dust just gets on that sensor! Dust is more visible when you have stopped down to a small aperture (high number) as the depth of field is much greater, but it can be visible in the sky, in particular, in shallower depth of field images. For some reason, I always seem to see them when I have created a panorama and so you get the same spot copied multiple times across the image!
They may not look like much in this full resolution crop, but in Lightroom (if you select the dust spot tool and press A), you see them in all their glory:
That dust spot tool does a great job of removing them, but how to I get rid of the dust before I go out on a shoot? First, I have never put anything damp anywhere near the sensor – no blowing on it with your mouth to remove some dirt, no wet cleaning products. And no changing lenses when it is foggy or raining! So my sensor is still pretty pristine as it came from the factory. But dust still gets in there and although you can use a blower, I always think that blows the dust about inside the camera so that it is able to find its way back to the sensor when you least want it there!
I’ve had a lot of success, instead, with the Visible Dust butterfly brush. There is an expensive one with LED lights, but the basic one that costs about $60 is good enough for me. Basically it is a nylon bristle brush that spins at high speed and the friction between the bristles creates static on them. When you lightly dab the sensor with the brush, it attracts the dust and you remove it that way. A quick whizz round again throws the dust away. I never touch those bristles as that could introduce finger or skin grease onto the sensor and as long as you keep it dry and free of anything sticky, then the dust shouldn’t stick. I do have a magnifying glass with LED lights that is sized to cover the lens mount and those two things go with me on every trip. There are much cheaper versions of the loupe, but I went with the Visible Dust one and it has proved very reliable.
Finally, if all goes wrong and things get stuck on your sensor, read my horror story about my earlier Sony A7Rii here!
Hope this helps!