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Aircraft propellors frozen in video.

Explorer ,
Oct 06, 2020 Oct 06, 2020

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I know this is obviously a product of shutter speed against the RPMs of the propellors,and choosing a different shutter speed won't work as they vary the speed of the props.
Is there a way round this? I thought of maybe taking some stills with slow shutter speeds and layering them over the top of the video props.

 

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Community Expert ,
Oct 06, 2020 Oct 06, 2020

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AFAIK, there is nothing you can do about it now. Someone with better skills in After Effects may hopefully chime in.

 

Regarding shutter speed:
If i shoot 25 frames per second i generally use a shutter speed of 50. If using higher the motion in the video looks "nervous" and un-natural to my eyes while slower tends to smear out everything when the camera moves or when there is lot of motion going on. Do some tests if possible and see what you like best.

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Thank you.I have to wait until next year now for the next engine run to try different settings.

Has anyone else got any ideas please?

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Edited down to a relevant clip for anyone who doesn't want to watch all of it......

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Advisor ,
Oct 06, 2020 Oct 06, 2020

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That's tricky. I've read, tested, and asked pro DP's about this stuff and it's still impossible for me to understand. So I won't be much help if at all. I think what you're looking for is the old filmic look ( film cameras with 180 deg shutter shooting 24fps ) so the props blur out at high revs. So, the obvious solution is to shoot film at 24fps, but good luck with that. Probably can't find cameras, film, labs to process film, make work print, do telecine to digital, etc. A non starter.

Don't know what camera you used but it looks like global shutter ( not rolling ). If it was a slow rolling shutter the blades would have curved.

Some people say a fast rolling shutter is more like film ( some blur like you want but no curving ).

 

The shutter speed and revs have nothing to do with the solution... it revs higher, you get more blur. It idles and you get less blur. Just like old film.

 

But the shutter speed DOES have to do with how much blur you get so I would shoot 24fps or 30 in NTSC land, 25 fps in PAL land.

 

Those guys are probably reving up just to test the magnetos... each engine has BOTH, LEFT, and RIGHT magneto posistions on a switch. It has to be tested at a certain rev.. and it runs on BOTH... but for safety the need to switch to left and then right and back to both. The plane flies with BOTH. That looks like what they were doing.  So it never got up to take off revs.... not enough to taxi and then take off, etc.

 

So, I really don't think it looks bad at all.

 

🙂

 

 

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Community Expert ,
Oct 06, 2020 Oct 06, 2020

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24p is definitely not the magic solution and won´t magically fix an issue like this when filming. The key, no matter the frame rate, in situations like this is the sutter speed. 1 frame per second is not the difference between what the YouTube video shows and perfect spinning propellers on video.

 

🙂

 

 

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Advisor ,
Oct 06, 2020 Oct 06, 2020

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thanks Averdahl, I kinda assumed people would use the 180 deg shutter so at 24 the shutter would be 1/48th.... just like you shoot 25 fps at 1/50th

 

: )

 

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Taken with a Panasonic Lumix G9.
They're not testing the magnetos as such as it's startable but not in airworthy condition because of lack of vital spare parts.The museum in question have to be able to start some of their aircraft to maintain museum status (a bizarre pact with the local council for them to be allowed to stay open).So they start this and an English Electric Lightning on specified weekends a few times a year.The entry fee they charge goes towards keeping the museum open as the rely entirely on voluntary donations and gate money.

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Advisor ,
Oct 06, 2020 Oct 06, 2020

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I don't know if this note helps, but it might a little....

 

a film camera shutter is like a round disc with a pin in the middle and it spins around really fast. HALF the disc is gone ( which makes it a 180 deg shutter ). The film gate gets light from the lens 'through' the shutter.. which means half the spin moves through the film plane open and then the other half spins through and no light comes through ( that's when the next frame is pulled down into position for the next exposure ). So in essence the film is NOT exposed immediately but gradually as it spins through. It's such a short amount of time it's negligible but it does add to some artifacts when doing fast stuff. It even adds to that 'blur' effect via motion of props very slightly.  That's why some say a fast rolling shutter is more like film. Global shutter is closer to CCD than CMOS in a way...

 

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Thanks but I already know all that.I need to know how to get motion blurred props with my digital camera.

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Community Expert ,
Oct 06, 2020 Oct 06, 2020

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Both of the posted videos are variable frame rate. So just curious how you are shooting the videos, and also how you are exporting the edited pieces?

 

Parts of this look fine and parts look almost like stills. And the variable is how much they are reving the engines?

 

I'd try to shoot without the guy moving in the foreground. It might help to edit things together.

 

Stan

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Community Expert ,
Oct 06, 2020 Oct 06, 2020

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Both of the posted videos are variable frame rate.

 

I really doubt that VFR is to blame here. How do we even know that it is shot as VFR? 🙂

 

This Wikipedia article explains the issue and have an video example of a rotating airplane propeller: Wagon-wheel effect

 

"The wagon-wheel effect is most often seen in film or television depictions of stagecoaches or wagons in Western movies, although recordings of any regularly spoked rotating object will show it, such as helicopter rotors, aircraft propellers and car commercials. In these recorded media, the effect is a result of temporal aliasing.[1] It can also commonly be seen when a rotating wheel is illuminated by flickering light. These forms of the effect are known as stroboscopic effects: the original smooth rotation of the wheel is visible only intermittently. A version of the wagon-wheel effect can also be seen under continuous illumination."

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Thanks.I fully understand why this is happening,I just need to know if there's anything I can do to the video to make it look like how I see it with my own eyes.

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Shooting at 100mbps fixed and exporting variable as I hadn't thought to change it.

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Sadly I don't have special powers to stop the guy in the hi-vis from moving about while I shoot the video.He's the chief safety officer and is in charge of the start up and shut down of the engines,they can't do it without him or someone else there.

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Advisor ,
Oct 06, 2020 Oct 06, 2020

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I had the impression from the short youtube video that this plane was a museum piece, out for an annual certification of air worthiness re: standards it has to meet ( like FAA certification in the U.S. ? ). It's a beautiful airplane ( a monster ) and I think whoever sees the test at the museum and all the people who work at those places ( lots of volunteers for tours and history lessons ) will love what you did.

 

Good going !

🙂

 

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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It's a few times a year event when they run it up and an English Electric Lightning,both are startable but not allowed to get airborne.
An agreement with the local council means they have to be able to start something there to be allowed to stay open.

https://gatwick-aviation-museum.co.uk/museum/ 

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Advisor ,
Oct 06, 2020 Oct 06, 2020

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Thank you so much for this post and question. I will learn a lot when it's solved.

So far I haven't heard a single ' Thank You' to anyone responding, but have heard, ' I already know all that'.

So much for guessing and wasting time. I might try shooting stills like you said in the beginning or using radial blur keyframed with masks. Otherwise you're on you own champ, as far as I am concerned.

The only thing I learned so far is it's a GH5, whatever in god's name that is ....

 

Adios.

 

 

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Thank you for your concerns over my lack of use of 'thank you' on the previous page,but if you look back you'll see I actually said it three times (four if you include the above).

If the only thing you learned is that my camera is a 'GH5, whatever in god's name that is' you might want to read it again as I never said that.You must know digital camera model numbers to change G9 for GH5,so was there any point in saying this?

I forgot to say I did try radial blur but it looked terrible,but thanks for the suggestion.

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Advisor ,
Oct 06, 2020 Oct 06, 2020

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this is obviously a shooting problem and not a post problem and should go to the lounge or some other dark hole.

 

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Explorer ,
Oct 06, 2020 Oct 06, 2020

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Yes it's definitely a shooting problem,but because the propellor changes speed,it's something I have no control over so would like to find some way around this in post.It's a relevant question for this section of the forum,so why would you want it moved?

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