Many thanks for your delightful, thought provoking addition to this thread.
I'm beginning to suspect we share a common trait: Pursuing randomly occurring subjects of interest until we have explored them from several perspectives. As mentioned elsewhere in this thread, I tell people I do it to try and stay mentally alert (snicker, snicker ... ). What is your excuse?
You got me started thinking about a number of earlier helicopter images of mine, so I explored a few to see if I could draw any conclusions and correlations with your observations in this thread. See new thread here with discussion of each image and some tentative conclusions that fit well with your material here.
As mentioned earlier, I hope to obtain some real shaft rotation speed and rotor blade length figures during my next mission. Then, we can summarize the equations in their most concise form and carry them around in our heads, ready for use in a moments notice. Mental arithmetic is another thing I do to try and stay sharp.
I do shoot helicopters on the ground as well as hovering close to ground level, but much closer than I would be during air-to-air sessions. See image number 1 in the new thread.
Thanks again Neil for a wonderful addition to this discussion.
HBB in Phoenix, Arizona Nikonian Team Member
Photography is a journey with no conceivable destination.