Speed

Kevin Childress on October 20, 2011
Jeroen Verburg on October 20, 2011

I liked the original, but I really like your tour of remakes with the D7000. The colors are even better, and sharpness too. The silky water in the original was a nice touch though.

Kenneth Kruse on October 20, 2011

Below is my theorhetorical analysis conducted on the above image.

Based on Newtons law of universal gravitation where water falls at 32 ft/sec² and an approximate descent of 6 ft I have calculated the speed of the drive wheel to be 181.5 RPM, given an established gear ratio of 0.092 and a final drive speed of 1972.8260869565217391304347826087 RPM. Multiplied and then divided again by the shutter speed of 2.5 sec as supplied by the EXIF data I have concluded that exposure of this image is within +/- 0.000001 EV from perfect!

David Brown Photogra… on October 20, 2011

Hahahahaha...... I think Ken has way too much time on his hands now that the nights are drawing in !

:o)

However this is a very nice image Kevin isn't it?

Maybe a bit of spoke blur would communicate the speed better. So I reckon slow it down to a second or so. See what Ken comes back with.

Jethro

Kevin Childress on October 20, 2011

Jeroen, Thank you for the note on the original. I have at least a dozen new compositions of this wheel and the original is still my favorite. And thank you for the note on the image quality - it is far superior over the Kodak and Fuji!

Ken, WOW, great minds really do think alike! It is amazing that I used the same calculations but you missed a couple of key elements: We must also consider that at 09:20 and 34 seconds at my mapped position, the sun was at 118.9 degrees azimuth and +19.9 degrees altitude. Given this, combined with the lens position of +1.5 feet change in elevation from the center of the wheel, and my distance and bearing of 48 feet at 294.8 degrees from the subject, we come to the exact same number of +/- 0.000001 EV. But unfortunately when I factor in the large blind of trees at my back, the 2.5 second shutter speed pushes the number to +/- 0.0000015 EV overexposed. DAMMIT, MAN!

But I'm prolly missing something somewhere. We better get Jethro and Austin over here to check it out. Let me go get 'em!

David Brown Photogra… on October 21, 2011

Did you allow for gravity and the effect of anything massive (local mountain, Chevy Suburban, things like that) might have.

Also Ken didn't allow for the latitude of this shot and the deviation that would cause on the speed of descent. The closer you are to the equator the further you are from the center of the earth.... but I don't need to explain that to your great minds.

It still makes my head spin..........

Jethro

© Tom Cooper on October 21, 2011

It's worse than you think, Kevin. I see no mention of the ambient temperature. Despite the camera's recording of the shutter speed, all shutters have moving mechanical parts. As the temperature increases, the viscosity of the lubricant drops, causing a slower shutter speed. The National Weather Service only has 3 days of history on-line, so I could not go back to 9:20 on 10/17/2011. Assuming the next day was approximately equivalent, the temperature at 9:33 am on 10/18/2011 was 66°F. This would be slightly lower than the typical design temperature of 21°C, resulting in a shutter blade movement that is slightly slower than ideal. Depending on the shutter design, this should result in a longer exposure than reported. My estimate is that you are actually over by about 0.0000019 EV. Of course, this assumes that 1) The weather was the same on both days; 2) The camera had adjusted to ambient temperature; 3) No internal factors warmed the camera, such as operating electronics or batteries; 4) The sun was not shining on the camera.

Since odds are assumptions 1, 2, and 3 are probably not valid (I see no evidence in the photo of direct sunlight, so assumption 4 seems to be supported by the evidence), that would lead to the possibility of the shutter operating at a temperature slightly warmer than design, and therefore the image might just be as much as 0.0000006 EV under.

Kenneth Kruse on October 21, 2011

Ah but those Japanese are brilliant, they have actually factored Time/Date/Temperature data into the exposure algorithms. Although it appears Kevin did not have the optional GP-1 GPS unit the D7000 defaults to Tokyo values which happens to be 67ºF at the recorded TV for a mean deviation of 1 × 10-8 s. Gentlemen I stand by original assumptions. Of course there is also the drag coefficient of the shutter plane moving through the above normal barometric pressures recorded on said date but lets not get technical about it.

Kevin Childress on October 21, 2011

HAHAHAHAHA ! What a hoot! These are good times ...

© Tom Cooper on October 21, 2011

Did anyone consider relativistic frame-dragging caused by the motion of the wheel itself?

Kevin Childress on October 21, 2011

There they go again ... taking my theories and claiming them as their own ...

:)

Kenneth Kruse on October 21, 2011

Did anyone catch my theo-rhetorical preface? It was not a typo but a new word I made up just for this image. When you guys see this in a dictionary a few years into the future I hope you remember this conversation!

Kenneth Kruse on October 21, 2011

Sorry for the previous digression, I think Austin is on to something. Frame-dragging would definitely warp the space-time continuum enough to have a measurable effect on exposure, however, current string theory suggests that the relative consciousness of the initial viewer would factor any possible deviation into ones current conscious state thereby negating any possible adverse effects within this reality, the theory does however allow frame-dragging to adversely effect the exposure within nieghboring parallel realities. In summary, using string-theory as a working hypothesis, since Kevin was likely the initial viewer of the captured photons, Kevins conscious awareness at the moment of capture and more importantly the moment of initial viewing was obviously favorable to the outcome, since all others are in obvious agreement on the outcome of the captured photons it adds further validity to the currently hypothetical string theory. I think this warrants further research.

Kevin Childress on October 22, 2011

... I think I'll go back to my landscapes now ...

:)

David Brown Photogra… on October 22, 2011

Damn.... and I was most of the way through my research into Planck's constant and its affect on light compression.

Next time huh?

Jethro

Kenneth Kruse on October 22, 2011

Thanks for letting me vent.....obviously there was plenty of hot air to rid myself of!

Photo taken in Burks Fork, VA, USA

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• Uploaded on October 20, 2011