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Topic: Visible Airflow: How To Get It?
Username: teopilot
Posted 2010-10-30 04:50:26 and read 6330 times.

Hello Airliners.net Fellows!

Here I am to ask you a quesition...

I have been wondering so long how it's possible to get such an inclredible shot like these ones:

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Photo © Ronald J Stella
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Photo © Tomas Cologan


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Photo © Tim De Groot - AirTeamImages
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Photo © Fabricio Jiménez



First of all: I know all depends on meteorogical conditions...
but which are the conditions needed so that the fluid ( the air) comes visible as vapor above the wing, or as a "vapor vortex" between the wing and the leading edge and out of the wingtip? ( as you can see especially in the first two shots)

then, I'll refer now to the last two pictures, especially the last one:
how may I get that spectacular background effect of the aircraft's airflow? I think that low clouds are needed...

thank you in advance,
Matteo Stella

Topic: RE: Visible Airflow: How To Get It?
Username: viv
Posted 2010-10-30 07:27:11 and read 6292 times.

High humidity and high angle of attack.

Topic: RE: Visible Airflow: How To Get It?
Username: teopilot
Posted 2010-10-30 09:26:46 and read 6243 times.

And what about a rainy day? (because tomorrow I'll go spotting in LIMC (Milan Malpensa) and weather forecast says "rain")
Would it be ok for my purpose?

Topic: RE: Visible Airflow: How To Get It?
Username: alevik
Posted 2010-10-30 09:48:57 and read 6237 times.

Rainy days are definite high humidity and if you are shooting aircraft on approach it is possible.

I would caution to temper your expectations of achieving photos suitable for upload here on anet in rainy conditions. It is best to master the ability to get uploads in good conditions before trying the trickier conditions of overcast, rainy, snow or night shooting. Practice does make perfect and rainy days can produce some stunning images, so hopefully you get the experiences and opportunity you want at LIMC.

Pete

Topic: RE: Visible Airflow: How To Get It?
Username: user47
Posted 2010-10-30 10:13:20 and read 6231 times.

Rain is a real pain. I've had my best luck on days with mist or shortly before/after a rain. Low clouds or even foggy conditions are a huge help. Keep in mind you'll be dealing with low-light conditions. Crank up the ISO, use a higher aperture, shoot raw-- Whatever it is that you do to make sure you achieve a quick shutter.

I've found that I'm more satisfied going into any photography situation with the expectation of mediocrity. Not because I expect such quality from myself but because it's better to level-set expectations. Just a small percentage of photos are going to yield the wow factor. It's easy to get discouraged going in with the expectation of achieving such great work as featured here on Anet.

Topic: RE: Visible Airflow: How To Get It?
Username: teopilot
Posted 2010-10-30 10:39:18 and read 6225 times.

Thank you for your advice and opinions.

I Have linked those photos only because I think they are really good, and I'm still far from that ability... but I have to try and try to get more experienced.
I know that when I'll look over the photos I'll take Tomorrow, most of them will be "rubbish", due to the bad light which comes with a cloudy day.
But I'll go there just to try to turn out something good... I hope my good purposes might be satified by Tomorrow.  

As you said, a good way to learn the "know how" is only by trial and error, and I definitely agree with you!

but now, let's go back to the questions...
You mentiones that is common to see them on a landing aircraft... what about departing ones? It may be the same, I suppose...
then, is the phenomenom we are talking about "continuous" or is it very quick? I mean, is it needed a good timing ( where good timing means to act before it happens, so, I'd shoot with the hope to get it) or can I start shooting only when I see this effect?

Topic: RE: Visible Airflow: How To Get It?
Username: user47
Posted 2010-10-30 11:32:13 and read 6206 times.

In my experience the streamers off the wings are pretty constant. When conditions are appropriate for them to form they appear for at least a few seconds, of not longer. Other vapor halos last only moments. There are quite a few examples on anet and flickr of a mini tornado forming in front of an engine while on the ground, those are very rare and hard to catch since you'd need to be on the tarmac with the plane. Aside from that aberration I've never seen other distortions from on ground or departing aircraft. I'm sure they form but I haven't seen them. I'm also a bit biased. I tend to see arrivals only at my home airport.

Topic: RE: Visible Airflow: How To Get It?
Username: tadeuprimo
Posted 2010-10-30 15:35:18 and read 6140 times.

In the landing you have more drag, this phenomenon will happen at this time with more frequency.

Cheers

Topic: RE: Visible Airflow: How To Get It?
Username: Psych
Posted 2010-10-30 15:44:49 and read 6136 times.

Hello Matteo.

As described, the effect can be seen on departure and arrival - but the effect above the wing is often very quick - a second or so:


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Photo © Paul Markman
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Photo © Paul Markman



I remember in these two photos the effect was gone in a flash. You need your shutter finger to react quickly, or just get lucky.

I used to know exactly how these effects were caused in my youth when I studied physics, but time and age have made things a bit hazy. All to do with vapour pressure etc   . But as has been described you are looking for days when the moisture content is high.

As for the effects in those last photos you linked (and often seen in the great photos of Steve Morris) - you are probably most likely to see that when there is moisture in the air in the form of cloud/mist/fog at low level, which then can be disturbed by the airflow caused by the wing flying through it. A 'normal' cloudy day won't be enough. I have yet to photograph that unfortunately.

Enjoy your day.

Paul

Topic: RE: Visible Airflow: How To Get It?
Username: cpd
Posted 2010-10-30 15:51:30 and read 6134 times.

One of those photos is backlit - so unless there is some pretty magical motive (in which the example does have a great motive), you might find yourself getting an image rejected for dark.

I've done a few images with highly visible fog/condensation trails. MD-11 is good for it, as is A380 and A330 Airbus (particularly A330 for the condensation trails streaming from the winglets).

In my cases, I generally took those photos shortly after rain, say, within about 5-10min after it stopped raining.

In darker conditions, make sure you get the exposure right - the shadow areas can be very noisy. You don't want to have to artificially brighten the image in Photoshop - that will make the noise even more apparent.

Quoting teopilot (Reply 5):
You mentiones that is common to see them on a landing aircraft... what about departing ones?

Very common:


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Photo © Chris P Denton
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Photo © Chris P Denton



C130 Hercules and Dash-8 Q400 planes are great to get those spiral streams of condensation whirling off the tips of the propellors. This is a great effect to get, but you'll need a low shutter speed to capture it.

[Edited 2010-10-30 16:20:18]

[Edited 2010-10-30 16:23:25]

Topic: RE: Visible Airflow: How To Get It?
Username: RonS
Posted 2010-10-30 15:57:45 and read 6131 times.

Quoting teopilot (Reply 5):
what about departing ones?


The Airfrance was a departure. It was also shot in light steady rain and mist on a humid day.
Quoting teopilot (Reply 5):
is the phenomenom we are talking about "continuous" or is it very quick



When it builds up on the wings in my experience it is very quick. It builds then blows off, builds then blows off. I don't often have much luck, but when I do I possibly get one keeper in a sequence, if that.

Quoting alevik (Reply 3):
It is best to master the ability to get uploads in good conditions before trying the trickier conditions


Agreed. Your recent uploads have been nice to see. Once you got the sunny day moving aircraft stuff down pat, keep pushing your limits. Start lowering the ISO on those nice days, raising the Aperture and perfect your panning motion. Because like what was said above, you're generally going to be using slower shutter speeds, I think that AF was under 1/200th at ISO 320. My ISO 400 ones are quite grainy (although I will adamantly say that most of the grain is rain!)

On that particular day I shot 5-6 other aircraft departures with which had significant condensation, approx 8-10 shots each and only one suitable for upload. I have maybe 1 other photo from this day that may be salvageable and I'll rework it when I'm board.

Quoting teopilot (Reply 5):
or can I start shooting only when I see this effect?

Well you'll know on these humid days what to look for. If you see it on a 757 when you get to the airport, and next to go is another similar type of aircraft or larger, start snappping away. In my experience you can't wait till you see the condensation to take the photo, it will be gone...but may build back and blow off again within a few seconds. Best to just snap away.

I shot it in Continous mode, so I take a bunch, in this case probably 10 of the air france and only got one I thought was good enough quality.

Topic: RE: Visible Airflow: How To Get It?
Username: teopilot
Posted 2010-10-31 10:24:46 and read 6029 times.

Thank you very much for your advice!!! I really appreciated it!  

Well, Today I went to my "destination", where I spent about 3 hours of spotting...
Light condition was quite prohibitive... so I shot in Aperture priority at f/7.1 - f/8... and shutter speed was likely from about 1/60 and 1/125.
I have a lens without stabilizer, so shooting at hingh focals with slow speeds are very hard, but I gave it a try: it would be a nice condition to practice some panning!
Well, traffic was ok, with several heavies landing, and I think I'll turn out something good.
Out of 150 shots, maybe about 20 will be acceptable...
And, of course, I was able to shoot my target!!!
Really, I'd say that as the first time I could be satisfied  ; then I'll have only to continue practicing...

Could anyone tell me the exact physical explanation for this phenomenom?

Topic: RE: Visible Airflow: How To Get It?
Username: RonS
Posted 2010-10-31 11:56:58 and read 6016 times.

Quoting teopilot (Reply 11):
I have a lens without stabilizer, so shooting at hingh focals with slow speeds are very hard

The below photo was shot without a stabilizer (70-200 f/4 non-IS), at 1/60th, near 200MM, so certainly attainable.


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Photo © Ronald J Stella

Topic: RE: Visible Airflow: How To Get It?
Username: spencer
Posted 2010-10-31 12:39:08 and read 6008 times.

From personal experience AMS is by far the best place I've witnessed this effect. Having said that on a very cold British morning a couple of years ago, I witnessed LHR arrivals with similar effects. I'm assuming there was saturation in the air as there was certainly no heat!

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Photo © Spencer Wilmot
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Photo © Spencer Wilmot


Also at LHR, by two other photogs (and a couple of my favourite photos too, might I add).

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Photo © Harm Rutten
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Photo © Stuart Yates


Just to echo Paul's thoughts, yes you need to have a quick shutter finger, it comes and goes in the blink of an eye. Vortices stay longer however.
Spence.

Topic: RE: Visible Airflow: How To Get It?
Username: Psych
Posted 2010-10-31 13:27:24 and read 5986 times.

Quoting teopilot (Reply 11):
Could anyone tell me the exact physical explanation for this phenomenom?

I will make an attempt Matteo, but as I said above my days studying physics are decades behind me, so apologies in advance to those with a better knowledge than me for any factual errors.

Basically a wing works by forcing the air above its surface to travel faster than that below (the shape makes the air molecules above travel a longer distance than those below (once 'split' by the leading edge)). Faster moving air creates a lower pressure (and density), so the pressure below the wing is higher, and this is the main source of 'lift' - pushing upwards into the area of lower pressure. It is a little more complex than this to explain all the lift, but for now that will do. Check out Bernoulli's principle.

Lower pressure does a number of things, including cooling the air. A bit like taking energy out of the molecules. Energy is required to keep the water molecules in vapour form, and when the temperature reaches the 'dew point' - the temperature where the water molecules condense out and cannot be held any longer as vapour. - the water molecules condenses out to form a 'cloud' of droplets.

If the weather is such that there is a lot of moisture in the air - e.g. the temperature of the air is close to the dew point - then the brief reduction in temperature above the wing can be enough to trigger the formation of a mini cloud. Bear in mind that warmer air is more capable of holding the water as a vapour - warm, muggy days mean there is a lot of water in vapour form kept from condensing into droplets by the 'energy' of the warmth.

I am in danger of starting to confuse myself here - never mind you - so I will stop there. I hope this is of some help.

Cheers.

Paul

Topic: RE: Visible Airflow: How To Get It?
Username: JohnKrist
Posted 2010-10-31 14:29:18 and read 5965 times.

It's the same effect that creates clear and overcast skies actually, low presssure creates rainy overcast skies, and high pressure creates clear blu skies. As Paul wrote, the pressure above the wing, or in the wake of the wingtip, is lower than the pressure of the air next to it, this creates condensation/clouding over the wing.

Here's a nice little video with cheesy music to show the phenomenon  http://www.youtube.com/watch?v=z4M1Rr3SWIg

Topic: RE: Visible Airflow: How To Get It?
Username: Geezer
Posted 2010-10-31 18:42:31 and read 5933 times.

[quote=Psych,reply=14]
I am in danger of starting to confuse myself here - never mind you - so I will stop there. I hope this is of some help.

Paul; I think that was a wonderful explanation ! (and I don't think you are the least bit confused, lol !)

A number of years ago, I was watching the Blue Angles perform at the Dayton Airshow; they had been flying the F/A-18 Hornet for a few years at the time. As far as I can remember, I believe it was a rather high humidity day; anyway, as the solo pilots pulled extremely high G, low level turns, they created all manner of "vapor" effects; also, within a second or so, there was a very audible "whooshing" sound; very exciting to say the least !

A few years later, I was visiting my son who works at the Naval Weapons Center, China Lake, Ca. I was standing on the upper level of the hanger, looking down on the activity on the tarmac, when a F/A-18 came in. I noticed almost the same effect as the pilot made a tight turn; a few moments later, the same plane taxied by, right in front of and beneath my vantage point, with the canopy up; A few moments later, I wandered back to my son's lab, and to my surprise, there was the same pilot, still in his flight gear, talking to my son . After a brief "intro", I asked him about the "vapor" effect; he did his best to give me a rudimentary explanation, but as I remember, he confused both of us !

As it turned out, he had just returned from a missile-firing test out on the test range, and was very excitedly describing it to my son; the "target" had been two old trucks, and he said both weapons had impacted within 6 inches of the aiming point ! It was the best opportunity before or since that I have had to ask questions of a Naval Aviator, immediately after having blown up two trucks with missiles !

So apparently, all this water vapor we see emanating from planes in flight is great to see, but very "tricky" to explain !
Charley

Topic: RE: Visible Airflow: How To Get It?
Username: Numero4
Posted 2010-10-31 21:14:08 and read 5908 times.

Quoting Psych (Reply 14):
I am in danger of starting to confuse myself here - never mind you - so I will stop there. I hope this is of some help.

Paul, your explanation is bang on. Having taken 3 classes of physical chemistry in university in the course of my previous studies, I was reading this thread in anticipation of someone explaining the whole thing in precise yet easy to understand terms, so I wouldn't have to go down that road myself. And you did it.

I'd add that when checking the airport local weather, I pay attention to the difference between actual temperature and dew point. When there's only a couple degrees C difference between the two and it's warm outside, conditions are favorable for vortices to form. The only ones I've witnessed consistently are the prop vortices on Dash-8s described earlier, and I actually didn't see them when they were happening, only when I looked at the photographs on the computer.

--Etienne

Topic: RE: Visible Airflow: How To Get It?
Username: teopilot
Posted 2010-11-01 00:33:59 and read 5889 times.

Thank you very much Paul...
Very good explanation! I Got it!  


Now, I'd like to share a shot I've just edited (I put it in the screening queue): the effect is quite visible, but I think the overall atmosphere is nice ( even the weather was horrible).
But I think it has something wrong, because I don't like it so much in the overall...
http://www.airliners.net/addphotos/b...ready/j1288548019.1531img_9015.jpg
I think more contrast and lightness are needed... what do you think about it? (sorry if I post here a shot in order to get a feedback, but as here we are...  )

In several other shot I took Yesterday the effect is even more visible, but let's start with this one!  

Etienne, Yesterday, I was very lucky, as I was able to see both with my eyes and my camera these effects, which lasted only when the plane touched down with the nose gear! 

Matteo

Topic: RE: Visible Airflow: How To Get It?
Username: cpd
Posted 2010-11-01 00:45:50 and read 5887 times.

Hi Matteo,

yes, I'm afraid, too little contrast - very tough conditions to get good photos in.

I think you need to look at the histogram, white/black points, and maybe adjust the mid-point to brighten that, but you'll need to do it on the original image. Quite soft too, as in looking blurry almost - but I guess that's the rain doing that.

[Edited 2010-11-01 00:51:26]

Topic: RE: Visible Airflow: How To Get It?
Username: teopilot
Posted 2010-11-01 00:52:20 and read 5884 times.

Quoting cpd (Reply 19):
Hi Matteo,

yes, I'm afraid, too little contrast - very tough conditions to get good photos in.

I think you need to look at the histogram, white/black points, and maybe adjust the mid-point to brighten that, but you'll need to do it on the original image.

Ok, so... I'll re-work on the original picture, taking care of getting that a bit brighter and more-contrasted  
Thank you!
Then, another question: does it seem soft in the left hand, especially nearby the tail?
Matteo

Topic: RE: Visible Airflow: How To Get It?
Username: cpd
Posted 2010-11-01 01:47:52 and read 5876 times.

yes, I see that as well, it looks like it may be blurry to me - but it could just be the rain causing that. I'll defer to more experienced eyes (ie, a screener) on that.

Regards,
Chris

Topic: RE: Visible Airflow: How To Get It?
Username: teopilot
Posted 2010-11-01 03:42:41 and read 5864 times.

Quoting cpd (Reply 21):
yes, I see that as well, it looks like it may be blurry to me - but it could just be the rain causing that. I'll defer to more experienced eyes (ie, a screener) on that.

Regards,
Chris

Yeah, I forgot to mention that it was raining a lot while I took that picture.  

Topic: RE: Visible Airflow: How To Get It?
Username: danpass
Posted 2010-11-08 16:59:06 and read 5636 times.

This past weekend I was at the Wings over Homestead air show in south Florida.

When these pictures were taken the weather conditions were:

Fair
72°F
Dew Point: 53°F
Humidity: 52%
visibility: 10.0 miles
30.07 inches and falling
Wind From N at 15mph


So the more humid the better but with enough angle of attack creating pressure differentials water vapor will form


(Exif is intact)

http://www.danpassaro.com/img/s8/v12/p71868284.jpg

http://www.danpassaro.com/img/s8/v9/p525015334.jpg

[Edited 2010-11-08 17:01:57]

[Edited 2010-11-08 17:03:01]

Topic: RE: Visible Airflow: How To Get It?
Username: Numero4
Posted 2010-11-11 14:56:29 and read 5537 times.

Quoting danpass (Reply 23):
When these pictures were taken the weather conditions were:

Says content is protected by owner.

Topic: RE: Visible Airflow: How To Get It?
Username: danpass
Posted 2010-11-11 17:40:24 and read 5524 times.

No edit button lol


here we go:



When these pictures were taken the weather conditions were:

Fair
72°F
Dew Point: 53°F
Humidity: 52%
visibility: 10.0 miles
30.07 inches and falling
Wind From N at 15mph


Topic: RE: Visible Airflow: How To Get It?
Username: soon7x7
Posted 2010-11-16 17:04:37 and read 5360 times.

Just watch humidity...this shot was recorded when temps on the ground were 11F. humidity levels occur at all temp ranges and cloud conditions...just watch overhead planes and if you see trails and vortices while they are at mid level...scream to the airport w/ you camera. (Low light helps...Backlighting)

recorded w 200-400 on jpg med as i was shooting ebay items


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