The many motion artifacts of Apollo TV
(from post #8203) It's already been determined that the flag started moving before he got close enough to it to touch it.
No, it hasn't.
It's important to remember the various artifacts of the Apollo TV system, especially as they relate to motion. Younger readers who may know only CCD cameras, LCD TVs and digital cable and broadcasting may be unfamiliar with these artifacts.
The Apollo TV system was entirely analog. As did all TV at the time, it used cathode ray tubes (CRTs) in both the cameras and the viewing screens. CRTs use electron beams ("cathode rays") accelerated by high voltage and usually steered by magnetic fields to scan the imaging target in the camera or the face of the viewing screen.
This high voltage is regulated but not perfectly. With a sudden change in scene brightness, the average beam current also changes and the high voltage can fluctuate. This causes the beam electrons to be deflected more or less than normal by the magnetic fields. This is visible as a momentary change in the
size of the image, a phenomenon called
blooming. It can happen in either the camera or the viewing screen.
When Dave Scott walks in front of the flag, the scene brightness changes very quickly and there does indeed seem to be a small amount of blooming that makes it look as though the corner of the flag is moving. The picture may actually just be changing size momentarily.
The other major artifacts in the Apollo TV system have to do with its unusual representation of color. Unlike the NTSC system used in the United States until just a few years ago, or the PAL and SECAM systems used elsewhere, Apollo used a
field sequential color system. Fields were successively exposed through blue, green and red filters (in that order) and transmitted as though it were a black and white signal. A special scan converter on the ground stored these images on a rotating magnetic disk and constructed a standard NTSC signal for broadcast. It is vital to understand that any given NTSC frame, which normally would be comprised of red, green and blue images exposed at the same time, actually consisted of blue, green and red fields
exposed 1/60 sec apart. This often caused moving objects to break up into colored "confetti".
Another complication is the effect of interleaving on the rendition of still frames used for analysis. Even in NTSC, the two fields that make a frame are taken 1/60 sec apart, so still-framing a moving object often results in it "vibrating".
And still
more motion artifacts would be introduced if the NASA Apollo TV archives were, as it seems, placed on film and then converted back to video.
The bottom line is that unless one is willing to analyze all these artifacts and complications along with a detailed generation history of the video being analyzed, one simply cannot conclude that the Apollo 15 flag actually moved a split-second before Dave Scott touched it. Since he clearly did touch it, Occam's Razor says that's why the flag moved; it's unnecessary to concoct any additional reasons.
delusion>
