Focal Length is another factor that can potentially affect the accuracy of focus. It is related to the lens of the camera we are using.
When the object is at different distance from the camera, we will need a different focal length of the lens in order to focus—meaning to clearly view the object. Therefore, you will need to know how to adjust the focal length, or else your photo may be so blur that the object cannot be clearly seen.
If you are not familiar with these, you can just use the auto-focus function of the camera and it will do all the stuff for you.