Find the aperture value at which your lens shows the best sharpness, and use this value whenever possible (most often it is f/8 or so).
If you don’t have enough light, or if you want to highlight the main subject using a shallow depth of field, increase the size of the aperture, but try not to open it completely unnecessarily.
If the need has come, feel free to open the diaphragm and do not worry about it. In situations where you may need it, the aperture value is not the most important factor limiting the sharpness of images. The wiggle spoils the image much more ruthlessly than any lens aberrations. Continue reading