Photography: Effects of aperture variation on sharpness

Taken with f5.6

Taken with f36

Either my concept is junk or my experiment. My knowledge says that a wider aperture would give lesser sharpness in the image regions where planes other than the focus plane is projected on the sensor, due to the wider light cone from these planes. When these cones meet the sensor they will be more spread out when compared to the cones from the same region when the aperture is smaller. But my experiments to prove this are telling a different story altogether.

To make the difference more apparent I selected the max and min apertures available in my camera in telephoto and kept the focus plane fixed, still I see a wider aperture giving better sharpness in all regions. Still, at this point of time I am more towards my concepts being true. My experiment turns out to be junk because in order to verify my concepts, the experimental setup should have had no other variables other than the aperture settings between the two shots. Here are the two things that changed between the two shots unknowingly.

1. Here I tried to shoot the clouds with min and max apertures and the shutter speed that I got was 1/80 and 1/4000 respectively. Even though the shots were taken only a few seconds apart we can easily see that the clouds have significantly changed their pattern in this time. This places a high probability of more cloud movement in the lower aperture shot than the wider one, which might have caused more blurness in the former.
2. Both the shots were taken with the camera hand held from on top of a pretty high building under windy conditions, which might have caused more handshake and in turn blurring in the lower aperture shot than the higher one.

I am not giving excuses for backing my concepts, I did not retake the shots with a tripod because I wanted a more practical, day to day effect of these values in photography. So even though conceptually a lower aperture would give more sharpness (proof pending), during practical day to day photography it is better to get a higher shutter speed just enough to keep any unwanted movements off our sensor.