Shutter Speed Propeller rotation equation

KHilton

I googled this and found this site with half the answer I was looking for, and that was this:

It is quite simple. (Number of Blades) * (Prop RPM / 60) will give you the denominator of the shutter speed.

For example, 2 blades, 2500RPM - The above equation gives 2 * (2500/60) = 83.33. This means that your shutter speed would have to be 1/83.33 sec or slower to get a full circle.

Another example, 3 blades, 2500RPM, requires 1/125th sec.

Dean

I was wondering if someone could help me further. We're looking for a half circle blur instead of a full circle. If someone could help me out in the format that Dean had posted this I would appreciate it

THoff

For a half-circle, double the shutter speed. What was 1/80 and 1/125 in the example above becomes 1/160 and 1/250.

JoeFernandezImaging

Remember this all depends on the setting of the throttle and the type of plane.

For example, a P-51 taking off has full RPM. You can shoot this at 1/60 or 1/125. On the other hand, a taxi shot you have to go lower, but it is still possible to get full circle.

On helicopters, most likely 1/60 or lower because the rotor action is slower than a prop even at high throttle. It is good practice. Try different levels with different planes and take notes for the future.

JoeFernandezImaging

Basically if the plane is at full RPM such as takeoff or air to air, 1/30 to 1/60 will get you full blur. If on the ground in idle, you may need to go to 1/15 to 1/30 and that can be a problem for sharpness. It also depends on the plane. For example - P-51 props are very fast at high RPM but C-130 or Huey helicopters etc are much slower. I just basically use that rule. This was done with a Sigma 150-500 hand held about 1/30 no vibration control and manual focusing and the results came out fine...

http://joefernandezimaging.smugmug.com/Other/Airshows/18197445_zTGMPc#!i=1768075803&k=5jcGwVP&lb=1&s=XL

flyvertosset

I googled this and found this site with half the answer I was looking for, and that was this:

It is quite simple. (Number of Blades) * (Prop RPM / 60) will give you the denominator of the shutter speed.

For example, 2 blades, 2500RPM - The above equation gives 2 * (2500/60) = 83.33. This means that your shutter speed would have to be 1/83.33 sec or slower to get a full circle.

Another example, 3 blades, 2500RPM, requires 1/125th sec.

Dean

flyvertosset

My teacher says set your speed at 250 and you will get prop blur, not full circle but 3-4 blades blurring nicely. Used this technique when shooting warbirds air to air and found it acceptable.