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<blockquote data-quote="Eyelight" data-source="post: 422394" data-attributes="member: 24753">I should reiterate the idea of using manual focus.&nbsp; I'm thinking the lens in use has a distance scale, so all you need to do is set it at or just inside the infinity mark.I also have some new, albeit old info, from my circa 1986 Kodak Professional Photoguide I located yesterday while rummaging through the gear box.The guide has a formula for calculating the stop-action shutter speed for a given distance, focal length, subject speed etc.&nbsp; Took me a bit to get it set up in Excel so I could see how it works.&nbsp; It uses the same CoC (circle of confusion) used for DoF and other blurry calculations.Cutting to the chase, I input the following:Distance = 34,000 feetSpeed = 400 MPH&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &lt;&lt;&lt;&lt; should be a bit high Focal Length = 240mm (DX)and the shutter speed outputted is: 1/84 secondsSo, theoretically if you were to set the camera on a tripod and catch the plane as it traversed the view, 1/84 second shutter speed would be enough to &quot;stop the action&quot;.&nbsp; I'd be real curious if this would work.Assuming the calculation is correct, what it means is, as long as the shutter speed is enough to overcome camera shake, it would be plenty to stop-action the plane.And I have an idea to check something.&nbsp; If the lens has a distance scale, point it at the clear blue sky and engage the AF while watching the scale.&nbsp; If the lens is trying to focus past infinity, that could explain how a missed focus at 34,000 feet is blurry.&nbsp; Someone else might confirm this, but I'm thinking the limit on the turn of an AF lens is actually past the focusing capability, so if the FP misses the airbus, you get the blur.</blockquote>

[QUOTE="Eyelight, post: 422394, member: 24753"] I should reiterate the idea of using manual focus. I'm thinking the lens in use has a distance scale, so all you need to do is set it at or just inside the infinity mark. I also have some new, albeit old info, from my circa 1986 Kodak Professional Photoguide I located yesterday while rummaging through the gear box. The guide has a formula for calculating the stop-action shutter speed for a given distance, focal length, subject speed etc. Took me a bit to get it set up in Excel so I could see how it works. It uses the same CoC (circle of confusion) used for DoF and other blurry calculations. Cutting to the chase, I input the following: Distance = 34,000 feet Speed = 400 MPH <<<< should be a bit high Focal Length = 240mm (DX) and the shutter speed outputted is: 1/84 seconds So, theoretically if you were to set the camera on a tripod and catch the plane as it traversed the view, 1/84 second shutter speed would be enough to "stop the action". I'd be real curious if this would work. Assuming the calculation is correct, what it means is, as long as the shutter speed is enough to overcome camera shake, it would be plenty to stop-action the plane. And I have an idea to check something. If the lens has a distance scale, point it at the clear blue sky and engage the AF while watching the scale. If the lens is trying to focus past infinity, that could explain how a missed focus at 34,000 feet is blurry. Someone else might confirm this, but I'm thinking the limit on the turn of an AF lens is actually past the focusing capability, so if the FP misses the airbus, you get the blur. [/QUOTE]

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