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Shutter speed for a heli ?

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AsRock

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Hello all,

Every so often i see this heli go over were i take some of my pictures and just woundering whot might be a good shutter speed so the roters get blur. As of last time it made it look like it was floating in mod air LOL.

Thank You
 
I reckon 1/100 for good blur.
--
Capturing Creation
 
I think it depends Highly on the speed of the heli.

I took this one from my desk at work, please look at the blur effect only vs. sharpness only. The picture it self is not great at all and c.af might have saved it, but no time for that at time of shooting. any slower would have been god, but I am afraid also blurred the heli completely not only the rotors.

Set it appropriate to the speed which it passes you. 1/100 will give a great blur, but might blur the heli as well.
[IMG= [URL='http://my.opera.com/Duplo/homes/albums/55368/Fly03_vga_framed.jpg]'] http://my.opera.com/Duplo/homes/albums/55368/Fly03_vga_framed.jpg] [/URL]

Shot at f/7.1 at 1/200, ISO200, AWB, manual exposure mode.

Take it for what it is just remember to factor in the speed of the heli when setting the shutterspeed.

Thomas
--
Nothing is foolproof to a sufficiently talented fool
http://www.my.opera.com/duplo
 
Here are two similar shots, one at 1/500 sec and one at 1/125 sec (both taken with FA*300 on a very dull day).

1/500 sec



1/125 sec



Even at 1/125 the rotor blades are not that blurred, I would expect that with SR you could reduce the speed by one or two stops without too much risk of motion blur as 'copters don't generally move that fast. But I haven't tried that out yet as I don't have a K100D (waiting for k10D).

I tend to use a tripod with a smooth action head, or at worst a monopod combination when shooting aircraft as I find this provides a reasonably stable shooting platform with lowish shutter speeds.

Difficult things aircraft, but one heck of a lot easier than birding!
--
Richard Day - 'Carpe Diem!'
Gloucester UK
 
Rotor blades move at between 250 and 500 RPM for typical helicopters.

Let's say the rotor radius is 20 ft and the rotor RPM is 400, then the rotor tips move at a tangential speed of around 800 fps. Depending on what you'd call "sharp", you should use at least something as short as 1/500 s to avoid blurring the blades significantly. 1/500 s would give 1.5 ft of movement, causing a typical rotor tip to move a distance equal to its own width. 1/4000 s would give only a couple of inches of movement.
 
richardday said:
Even at 1/125 the rotor blades are not that blurred, I would expect
that with SR you could reduce the speed by one or two stops without
too much risk of motion blur as 'copters don't generally move that
fast. But I haven't tried that out yet as I don't have a K100D
(waiting for k10D).

I tend to use a tripod with a smooth action head, or at worst a
monopod combination when shooting aircraft as I find this provides
a reasonably stable shooting platform with lowish shutter speeds.

Difficult things aircraft, but one heck of a lot easier than birding!
--
Richard Day - 'Carpe Diem!'
Gloucester UK
Click to expand...
I have the K100D, though I am waiting for the K10D too (bought the K100D before the K10D were announced),

I really ought to try that combination of c.af, low shutter and SR. But I am going to need a decent zoom lens (new DA*) firstly.

I will however try with what I got, I overlook the apron in Nuuk Airport from my desk.

A smooth action head tripod would be wonderful too, handheld, fast mooving objects and low shutterspeeds are a bad combination SR or not.

Thomas
--
Nothing is foolproof to a sufficiently talented fool
http://www.my.opera.com/duplo
 
It was taken at the Red Bull Air Race in the UK this year which didn't happen due to bad weather (high wind and rain). This 'copter was taking wind speed measurements at various heights.

It was a dreadful day, there were hoards of people and it took us over 2 hours just to leave the car park and then nearly another 4 hours to get home, normally under a 1 hour 30 minute trip.

The organisers had to refund all the visitors, a huge loss for all concerned.
--
Richard Day - 'Carpe Diem!'
Gloucester UK
 
The tips of rotorblades or propellors have to 'run' below the speed of sound, otherwise they lose lift. Sometimes you can hear the blades just breaking through the sound barrier, when too much lift is demanded. Usually the RPMs stay the same and only the pitch changes. So if you work on 333m/sec for the speed of sound, ignoring temperature etc, and say 300m/sec ( 1000ft/sec) to stay below that for optimum lift you can calculate your shutterspeed. Large rotorblades will have a lower rpm than smaller rotorblades, but the speed will more or less remain the same at the tip to give optimum lift. Then I think the only other things that come into the equasion is 2, 3, 4 or even 5 bladed rotors and how longer arc you want to see.

The more I think about it, the more complicated it gets!

Take a 4-bladed WASP, one I worked on years ago, with a rotor diameter of 9.82m. the circumference is then 30.85m say 30m for ease. So in 1/10 of a second it does one rpm. In 1/40 one blade has done a quarter turn and is at the position of the previous blade.

Just to give you an idea.

Hope I got it right. If not, I'm sure I'll be corrected.

Mike
--

 
Sounds to me like you got it right, but it demands a lot of knowledge about the various "whips" that you are trying to shoot. We have like four different main types in our company divided on different sub types. The "whip" will be long gone before I have the calculations ready...
Gotta work these out before shooting them..

Thanks for the equation though it is going to be useful:)

Thomas
--
Nothing is foolproof to a sufficiently talented fool
http://www.my.opera.com/duplo
 
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