Most people these days use the cameras in their cell phones. The auto focus mechanisms usually assume an object up close. They are good cameras for snapshots, but terrible for special circumstances. Also, people shake the camera all the time, but terribly so when they activate the shutter. It is rare indeed when someone can get UFO photographs while the camera is mounted on a tripod.
The objects in motion/flying may use an internal gravitational field which causes light to be ‘jumbled’ such that the object does not have a distinct visual feed. But that doesn’t fully explain the on ground visuals which are sharper.
Also the ionization of the craft’s skin tends to prevent sharp pics whenever the tech is operating.