2. The Aperture is Wrong
This brings us to cause number two: you haven’t chosen an optimal aperture.
While there isn’t one correct aperture in each and every scenario, you should understand how it impacts the image. When using an aperture such as f/2.8 the overall sharpness will be lower than when shooting with an aperture of f/13.
At f/2.8, the sharpest point may be razor sharp but the rest of the image is out of focus, resulting in a blurry appearance overall.
When using a more narrow aperture such as f/22, you’ll notice that the overall sharpness is reduced. While the image is in focus from front to back, it is less sharp than what it would have been at a wider aperture.
Finding the ideal aperture for each scenario can be tricky to understand but it becomes easier the more time you spend in the field.
Techniques such as focus stacking are helpful when photographing scenes that have elements both close to and far away from the lens.