The other I during a shoot in the north of Outaouais, QC, I found out that I had a huge dust speckle on my sensor. So huge that it was visible on the camera LCD preview (without zoom) and it was visible on the sensor itself.

So I used the spat-u-swab method: pec-pads, Eclipse solution and the "spatula". The first time it took me 10 time to get it right. This time it was done in one shot. I should note that the biggest photo store in Montréal had none of the pec-pads and eclipse. Almost shocking, I was not impressed.

Hint: when doing the test shot, close the lens as much as possible. Due to diffraction, the dust speckles are even more visible when the lens is stepped down. f/16 or f/22 seems to be a good value.