Dicky Howett's 1963 EMI 203 B&W image orthicon TV camera demonstration 1995 

They'd moved onto Vidicon (or similar) tubes by then.

Probably less than 3 hours maybe

"A side effect of the way the iconoscope works is an image that can never truly be black. Electrons will decay from the mica screen without any light hitting it at all--light simply accelerates this decay. The detector ring would pick these rogue electrons up, and it would transmit as an entirely grey screen. There needed to be bright areas of the picture to pull down the average emission of the mica screen and make the other areas appear black--in other words, high contrast scenery was required. Lighting conditions would have to be accounted for to keep the averaging effect of the iconoscope from producing odd images." From Technology Connections' video on Farnsworth and electronic television. The orthicon worked like the iconoscope in some ways, which I won't pretend to understand. But the gist is, absent contrast, any solid colour is transmitted as grey.

from wikipedia ( 7.2 Dark halo en.wikipedia.org/wiki/Video_camera_tube#Dark_halo ) This effect was actually cultivated by tube manufacturers to a certain extent, as a small, carefully controlled amount of the dark halo has the effect of crispening the visual image due to the contrast effect. (That is, giving the illusion of being more sharply focused than it actually is). The later vidicon tube and its descendants (see below) do not exhibit this effect, and so could not be used for broadcast purposes until special detail correction circuitry could be developed.

been researching a bit more. it's very complicated and this is just an educated guess: it's a photo-emissive system. it seems that the electron gun first charges the plate with electrons. then they're knocked off by brightness in the scene, and then the electron gun sweeps the image again to read it. (I think if there are already electrons on the plate the new ones bounce back, which can be read by a detector.) This means it's a negative image: black will be rendered by the places in the plate that still have electrons put there intentionally by the beam. The problem is that very bright light will introduce its own secondary electrons that did not come from the beam, and they will also be detected, which (I assume!) will overlay the negative image with a *positive*, blurry image. ...which is exactly how an Unsharp Mask/HDR effect in photoshop works!

Most likely the footage (I'm assuming you are talking about the LHO killing) were shot using a image orthicon TV camera.