Why UFOs are so difficult to see and capture in conventional cameras

Computer models have shown that very high intensity electromagnetic flux in a subdued mode does emit unpredictable visible spectrum of light. That is exactly what we humans can see in bare eyes. The glowing light unfortunately does not stay for long because the extra-terrestrial UFOs increase the intensity of the electromagnetic flux for stealth purpose after reaching the desired stable speed. That is the main reason why people sometimes see these glowing lights for a short while, and by the time they try to get a camera or other eyewitnesses, these lights are gone.
The high intensity electromagnetic flux that we are talking about, expressed in Maxwell or Weber is far beyond human imagination. Even the strongest super conductors that we know of are not capable of generating such high intensity electromagnetic flux.
In case of Extra-terrestrial aircrafts, the light that is visible comes from the subdued high intensity electromagnetic flux. The extra-terrestrial UFOs are mostly invisible. But the high intensity electromagnetic flux that surrounds them does emit visible spectrum of light when the flux intensity is brought down somewhat.