Re: For the black and white fans
I'm not Tim, but I can come up with a theory:. ;-)
First, there are obviously multiple light sources- several Sodium ramp lights on towers at various locations around the ramp? A few look significantly brighter than others. implying that these are the closest ones. The geometry between camera, prop "disk," and each individual light would give exactly one 'spark' from prop hub to the tip IF the exposure duration was such that only one blade passed between the camera and the sodium light source. Since the prop blade is a curved surface, the image of the sodium traces out a streak from hub to tip as the blade cuts across between the camera and light. Since the pitch is opposite on the front and rear prop blades, they produce very different reflection traces.
Second, since the exposure is longer than one prop blade (I believe its almost exactly one ROTATION of the prop so that all 3 blades of each prop cut between camera and sodium), each individual BLADE of the 3 on each prop creates its own "arc" of light. Subtle differences in the blades mean that each lamp image produces 3 very sightly different arcs grouped tightly together.
So- for each sodium light, there's a cluster of "arcs" for each front prop blade and each rear prop blade. For each cluster, there is an individual trace of each of the 3 blades on that prop.
Thinking this way is the curse of the engineer... Everyone else gets to say "oh, pretty" and get on with their day. I have to say, "oh, now WHY...." and waste 45 minutes thinking.
Oh, and maybe because I stared at it so long, this is so far my favorite photo from Reno this year.
Originally posted by Jan
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First, there are obviously multiple light sources- several Sodium ramp lights on towers at various locations around the ramp? A few look significantly brighter than others. implying that these are the closest ones. The geometry between camera, prop "disk," and each individual light would give exactly one 'spark' from prop hub to the tip IF the exposure duration was such that only one blade passed between the camera and the sodium light source. Since the prop blade is a curved surface, the image of the sodium traces out a streak from hub to tip as the blade cuts across between the camera and light. Since the pitch is opposite on the front and rear prop blades, they produce very different reflection traces.
Second, since the exposure is longer than one prop blade (I believe its almost exactly one ROTATION of the prop so that all 3 blades of each prop cut between camera and sodium), each individual BLADE of the 3 on each prop creates its own "arc" of light. Subtle differences in the blades mean that each lamp image produces 3 very sightly different arcs grouped tightly together.
So- for each sodium light, there's a cluster of "arcs" for each front prop blade and each rear prop blade. For each cluster, there is an individual trace of each of the 3 blades on that prop.
Thinking this way is the curse of the engineer... Everyone else gets to say "oh, pretty" and get on with their day. I have to say, "oh, now WHY...." and waste 45 minutes thinking.
Oh, and maybe because I stared at it so long, this is so far my favorite photo from Reno this year.
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