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TheSonntag
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Video Footage Of Typhoons Chasing A Tu-95

Thu Feb 19, 2015 1:38 pm

http://www.focus.de/politik/videos/v...-russischen-bomber_id_4487777.html

Interesting video, taken from the russian side. It seems there were not only Typhoons nearby, but some french plane, too. The Typhoons seem to be fully armed.
 
A320ajm
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RE: Video Footage Of Typhoons Chasing A Tu-95

Thu Feb 19, 2015 6:39 pm

Quoting TheSonntag (Thread starter):
The Typhoons seem to be fully armed.

This is definitely to be expected, as these aircraft would have been scrambled as part of Quick Reaction Alert.

Interesting video though!

A320ajm
If the British Empire and its Commonwealth last for a thousand years, men will still say, 'This was their finest hour.'
 
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Tugger
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RE: Video Footage Of Typhoons Chasing A Tu-95

Thu Feb 19, 2015 8:49 pm

I love how the video makes those big beautiful counter-rotating props appear to be moving very lazily!

Definitely an interesting video.

Tugg
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A320ajm
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RE: Video Footage Of Typhoons Chasing A Tu-95

Thu Feb 19, 2015 9:08 pm

Quoting Tugger (Reply 2):
I love how the video makes those big beautiful counter-rotating props appear to be moving very lazily!

The joys of aliasing!  
If the British Empire and its Commonwealth last for a thousand years, men will still say, 'This was their finest hour.'
 
epten
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RE: Video Footage Of Typhoons Chasing A Tu-95

Fri Feb 20, 2015 9:07 am

Quoting a320ajm (Reply 3):
The joys of aliasing!

Acutally, the joys of very short exposure times of each frame. Nothing to do with aliasing.
 
tommy1808
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RE: Video Footage Of Typhoons Chasing A Tu-95

Fri Feb 20, 2015 12:34 pm

Quoting epten (Reply 4):
Acutally, the joys of very short exposure times of each frame. Nothing to do with aliasing.

The sampling rate of the camera (=framerate) is lower then the frequency of the signal (=prop RPM). And that effect is aliasing. The short expose time only makes the effect so clearly visible.
If the camera would take enough pictures/second we would see a properly moving propeller.

Best regards
Thomas
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
steman
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RE: Video Footage Of Typhoons Chasing A Tu-95

Fri Feb 20, 2015 1:18 pm

Very interesting video.
I´ve never seen a fighter in operational service with a complement of 8 air to air missiles. I always thought that those kind of loads were exceptions and QRA units fly with a couple of short range missiles plus cannon and drop tank or a combo o short range/medium range missiles but not more than 4.
It´s good that NATO air forces show readiness. Cold war is over but we pay lots of money to be protected H24.
 
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RE: Video Footage Of Typhoons Chasing A Tu-95

Fri Feb 20, 2015 2:51 pm

Quoting tommy1808 (Reply 5):
The sampling rate of the camera (=framerate) is lower then the frequency of the signal (=prop RPM). And that effect is aliasing. The short expose time only makes the effect so clearly visible.
If the camera would take enough pictures/second we would see a properly moving propeller.

And if the camera frame rate equaled the propeller RPM, the propeller would appear to be stopped! That would be something to see! 
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flyingturtle
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RE: Video Footage Of Typhoons Chasing A Tu-95

Fri Feb 20, 2015 3:03 pm

Quoting Revelation (Reply 7):
And if the camera frame rate equaled the propeller RPM, the propeller would appear to be stopped! That would be something to see!

I've always loved seeing the aliasing effect in car wheels. The wheels stand still... I could watch this video for hours. Mostly because of the cool props!


David
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A320ajm
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RE: Video Footage Of Typhoons Chasing A Tu-95

Fri Feb 20, 2015 5:13 pm

Quoting epten (Reply 4):
Acutally, the joys of very short exposure times of each frame. Nothing to do with aliasing.


Unfortuntely you're wrong, but the guys above have explained why  

A320ajm
If the British Empire and its Commonwealth last for a thousand years, men will still say, 'This was their finest hour.'
 
GDB
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RE: Video Footage Of Typhoons Chasing A Tu-95

Fri Feb 20, 2015 9:44 pm

Previous footage of mostly civil aircraft intercepts have shown the Typhoons armed with 2 IR missiles and presumably the cannon, so seeing these with 4 AMRAAM and 4 of the short range IR ones is a departure.
Oh well, if the Russians insist these half baked attempts at intimidation whenever anyone in the UK says anything they don't like, the RAF can 'intimidate' back I suppose.
 
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garysted
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RE: Video Footage Of Typhoons Chasing A Tu-95

Fri Feb 20, 2015 11:09 pm

Gents,

I've photographed RAF Typhoon and previously Tornado F-3 QRA configured jets at Coningsby many times (most are on here). They virtually always fly with a full load of 4x AMRAAMs and 4x ASRAAMs. Even going back to the cold war days (I live just a few miles from a former RAF F-4 base) and QRA F-4s always flew '4+4'. For a few sorties some years ago I noticed QRA Typhoons sometimes loaded with only 2 AMRAAMS instead of 4 but that hasn't been the case for a while. I've never seen a example of any RAF QRA configured jet (even going back to the F-4) carrying just short range infra-red missiles when they were Sky Flash/AMRAAM capable. A few examples;


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Photo © Gary Stedman
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Photo © Gary Stedman


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Photo © Gary Stedman
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Photo © Gary Stedman



Gary

[Edited 2015-02-20 15:11:10]

[Edited 2015-02-20 15:14:21]
 
zkeye
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RE: Video Footage Of Typhoons Chasing A Tu-95

Sat Feb 21, 2015 12:31 am

Quoting Revelation (Reply 7):
And if the camera frame rate equaled the propeller RPM, the propeller would appear to be stopped! That would be something to see! 

Like this?

http://www.youtube.com/watch?v=R-IVw8OKjvQ&spfreload=10
Bring out the gimp
 
epten
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RE: Video Footage Of Typhoons Chasing A Tu-95

Sun Feb 22, 2015 3:37 pm

Quoting a320ajm (Reply 9):
Unfortuntely you're wrong, but the guys above have explained why

I'm the first to admit when mistaking, bu this time it is not the case. Aliasing is about artifacts. There are no artifacts here. The propellers are real.

http://en.wikipedia.org/wiki/Aliasing

Prove me wrong by pointing to a reliable source which will connect the term "aliasing" to a video of a "still propeller" or something similar, and I will be grateful: I am always eager to learn.

This is propeller aliasing:



The horizontal "blades" are not real. They are aliasing artifacts.

[Edited 2015-02-22 07:40:52]
 
A320ajm
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RE: Video Footage Of Typhoons Chasing A Tu-95

Sun Feb 22, 2015 4:13 pm

I'm a seismologist so deal with aliasing in my day job. This is definitely aliasing. I remember my professor at university showing us a clip of a helicopter taking off in front of a volcano (he was a volcanologist ha!). He asked us to explain about the blades appearing to move backwards and slowly. None of us knew. He explained it was aliasing. And that was our first ever lecture in signal processing.

A320ajm
If the British Empire and its Commonwealth last for a thousand years, men will still say, 'This was their finest hour.'
 
tommy1808
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RE: Video Footage Of Typhoons Chasing A Tu-95

Sun Feb 22, 2015 9:50 pm

Quoting epten (Reply 13):
Prove me wrong by pointing to a reliable source which will connect the term "aliasing" to a video of a "still propeller" or something similar, and I will be grateful: I am always eager to learn.

The link yout provided does that.

Quoting epten (Reply 13):
This is propeller aliasing:

It sure is. But in pictures like that you have a lot more going on than just aliasing.

Best regards
Thomas
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
jollo
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RE: Video Footage Of Typhoons Chasing A Tu-95

Mon Feb 23, 2015 12:25 am

Quoting epten (Reply 13):
I am always eager to learn.

Aliasing (or under-sampling distortion, or equivocation) is a general term referring to the consequences of Nyquist-Shannon theorem: any sampling at less than double the frequency of a signal (or, more accurately, the highest frequency spectral component of a signal) will lead to loss of information. How this lost information leads to distorted motion perception depends on many factors (not least how our brain works), but calling the "slow propeller" effect an "artifact" isn't incorrect: you're seeing "motion" that is only caused by under-sampling, and is not real after all. The apparent scimitar-bend of the propeller blades is also "not real" (see any picture of a parked Tu-95 for reference). The fast electronic shutter speed of the video adds to the illusion with apparently sharp edges and no motion blur.
 
epten
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RE: Video Footage Of Typhoons Chasing A Tu-95

Mon Feb 23, 2015 10:22 am

I am convinced. Thank you all!
 
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RE: Video Footage Of Typhoons Chasing A Tu-95

Mon Feb 23, 2015 1:01 pm

Quoting zkeye (Reply 12):
Quoting Revelation (Reply 7):
And if the camera frame rate equaled the propeller RPM, the propeller would appear to be stopped! That would be something to see!

Like this?

http://www.youtube.com/watch?v=R-IVw8OKjvQ&spfreload=10

Even though I do know what is going on it's still mind boggling, so thanks for posting that!
Wake up to find out that you are the eyes of the world
The heart has its beaches, its homeland and thoughts of its own
Wake now, discover that you are the song that the morning brings
The heart has its seasons, its evenings and songs of its own
 
tommy1808
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RE: Video Footage Of Typhoons Chasing A Tu-95

Mon Feb 23, 2015 1:36 pm

Quoting Revelation (Reply 18):
Even though I do know what is going on it's still mind boggling,

But the rolling shutter CMOS artifacts look just so much cooler... and a prop or helicopter with their vibrations are just perfect to produce wobble.

best regards
Thomas
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
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flyingturtle
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RE: Video Footage Of Typhoons Chasing A Tu-95

Mon Feb 23, 2015 1:46 pm

I'm quite a layman in these things, but this might clear something up:

It's quite simple. In some digital cameras, the picture is processed starting with the top left pixel. Then, all the sensor values are then read into a memory - top row, second pixel, top row, third pixel, and when that top row is finished, it begins with the second row, first pixel, second row, second pixel...

...this processing, line by line, happens while the propeller (or the rotor) in front of the camera is turning. This can lead to funny artefacts in digital photo cameras as well as digital film cameras.

Digital film cameras more or less have to work line-by-line. When the propeller makes a full turn in the time span from the top row, 483th pixel to the second row, 483th pixel (and so on until the bottom-most row), the propeller seems to stand still on the resultant film.

In modern digital photo cameras, you can expose all sensors at once, and the values are stored in the individual sensors until read out after exposure. So, you have at most the motion blur that naturally occurred with analog photo cameras. Here, you see normal motion blur, but no distortion:


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Photo © Angad Singh - Zone Five Aviation




David
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