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Posted on 04/07/14 4:26:58 PM |
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GKB
Magical Montagist Posts: 3953 Reply  |
Spinning propellers and things
After Friday Challenge #511 it would appear that I have been nominated by various members as the HTCIP guru for things aeronautical! There is a direct correlation between propeller rotation speed and camera shutter speed. As some of you will know I was a semi-professional air-to-air photographer when I wasn’t doing the ‘day-job’. This involved photographing many different types of aircraft in their natural environment – the air. Just one of the problems was the choice (or, more often, a lack of choice!) of a suitable camera plane. Due to the expense it was often the case that the maximum performance of the camera plane equalled the minimum performance of the subject aircraft. As a result I might be shooting, say, a Spitfire with a maximum speed in excess of 350mph from a Piper Aztec with a maximum speed of 140 mph; the Spitfire would have to fly at 140mph to remain in formation with the Aztec and so would be operating at a reduced power. If I could have a camera plane that had a high speed then the Spitfire would be able to use a high power setting. This would allow me to use a fast shutter speed and not have the problem of apparently stationary propeller blades. At the lower power settings, though, I had to be careful not to use too high a shutter speed as this would freeze the blades and look awful. The image below shows the aircraft that won the England – Australia race in 1934, the de Havilland DH88 Comet. As you can see the propellers show as a complete disc reflecting the sunlight from the front. This shot was taken at a shutter speed of just 1/200th of a second. Because the aircraft was actually flying at a high power setting (fast camera plane) the shutter was open for at least a half revolution of the prop and shows as a complete disc. 
The next image shows a B-24 with a B-17 behind (the sight and sound as they flew alongside was rather more than impressive!). Both aircraft are powered back as they fly alongside the camera plane which had a maximum speed of some 140mph. The shutter speed was 1/500th of a second giving a nice blur to the propellers but not freezing them. 
One thing to note is that the blur increases towards the prop tips due to their higher rotation speed. Replicating this blur in Photoshop is quite simple and the basic technique is to copy the stationary blades onto a new layer and delete the original, filling in the missing bits of cowling as necessary. In CS6 or earlier just go to Blur>Radial Blur and select a value; CC has a different way of doing this but I shall assume that not everyone has CC. The important bit is to use the window in the Radial Blur dialogue box and drag the centre of the dialogue box to where you think the centre of rotation of the propeller is; if you don’t do that you blur won’t be correct. I was a naughty boy and didn’t do that so my blur is a little offset. You’ll see what I mean when you do it. In CS6 and earlier there is no live preview so you will have to guess at the amount of blur, hit OK and if you don’t like the result it’s Ctrl-Z! Because of the amount of blur that you use you might need to duplicate the layer or add a curves adjustment to darken it in order to see the blur. You might like to make a separate copy of the un-blurred blades and give this just a small amount of blur and possibly reduce the opacity. Try it; if you don’t like it then throw it away. Someone mentioned to me in a PM about trying to remove all those little cones on the prop spinner of FC#511. The reason that you can see them is because the spinner is highly polished – it’s a mirror! Hold a mirror in front of you and rotate it. You don’t rotate with the mirror. It’s the same with a rotating spinner. It reflects the surroundings; it’s also highly convex, even more so than the mirror in FC#509. To replicate this all I did was to copy the background image of the sky and Filter>Distort>Spherise it a few times, copy a circular section and scale it to fit over the original. As spinners are not a perfect surface you might just want to lock the transparency of the layer so that you don’t get a blurred edge, and give it the tiniest amount of Gaussian Blur. _________________ It only seems impossible. |
Posted on 04/07/14 4:27:30 PM |
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GKB
Magical Montagist Posts: 3953 Reply |
Re: Spinning propellers and things
_________________ If at first you don't succeed then skydiving is not for you. |
Posted on 04/07/14 4:27:51 PM |
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GKB
Magical Montagist Posts: 3953 Reply |
Re: Spinning propellers and things
_________________ If at first you don't succeed then skydiving is not for you. |
Posted on 04/07/14 5:21:41 PM |
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Steve Caplin
Administrator Posts: 6977 Reply  |
Re: Spinning propellers and things
Is that the same Grosvenor House that won the Mildenhall to Sydney air race in the 1930s? |
Posted on 04/07/14 5:31:45 PM |
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GKB
Magical Montagist Posts: 3953 Reply |
Re: Spinning propellers and things
It is indeed but the race was to Melbourne to clebrate its centenary. It is resident at The Shuttleworth Trust at Old Warden airfield in Bedford. There are plans to put it back into the air again sometime but I'm not sure of the timescale. Anyone who would like a day out watching vintage aircraft flying from an old grass airfield can do no better than a summer's day at an Old Warden flying day. _________________  |
Posted on 15/10/14 1:58:56 PM |
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DavidMac
Director of Photoshop Posts: 5472 Reply  |
Re: Spinning propellers and things
I am replying to a very old post here but I only just looked at it. Since you appear to be interested in things aeronautical and were once an air to air photographer this might interest you. My uncle Christopher (Bunny) Currant was a Hurricane pilot in WW11. Some years ago the hurricane he flew was discovered abandoned in Mumbai in India. It is known to be very same one he flew from its registration number. It has now been restored and is for sale. If you happen to have a spare £2,500,000 (+VAT) lying around it could be yours! You can find the plane and the story of its restoration here. _________________ The subtlety and conviction of any Photoshop effect is invariably inversely proportional to the number of knobs on it ....... |
Posted on 15/10/14 4:00:02 PM |
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GKB
Magical Montagist Posts: 3953 Reply |
Re: Spinning propellers and things
Aaahh ... if only! There are three WW2 aircraft I would love to have flown; top of the list has to be the Mosquito but the Hurricane comes very close behind knocking the Spitfire into third place. It's paying the VAT that puts me off buying it 
Thanks for posting that David. _________________ You're never too old to learn something stupid. |
Posted on 15/10/14 4:02:50 PM |
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GKB
Magical Montagist Posts: 3953 Reply |
Re: Spinning propellers and things
Forgot to mention ... on the German side the FW190 was a superb flying machine! _________________ You're never too old to learn something stupid. |
Posted on 16/10/14 1:24:43 PM |
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DavidMac
Director of Photoshop Posts: 5472 Reply |
Re: Spinning propellers and things
The first time in my life I ever went up in a plane was as a young twenty four year old cameraman. It was with the RAF Red Arrows. Folland Gnats if I remember correctly. A kind of bright red jet propelled airborne sports car. Very compact. Never have flown in anything in my life I was blissfully unaware of what I was about to let myself in for. After signing the blood chit, which relieved the RAF of any responsibility, I came out looking every inch the hero in a smart flying suit, bone dome under one arm, camera under the other. 
In my naive and innocent euphoria I failed to take in the significance of money changing hands between the other pilots and ground crew. 
The first couple of minutes were some of the most exciting of my life!! WOW!!!!! 
Then we hit the first loop ....... 
As the plane rose into the first half I found myself pressed deeper and deeper into my seat by the increasing G force. Then we hit the top and the plane did a stomach lurching flip over and suddenly the G is all negative and I rose out of the seat held in place by the harness. 
Sadly my lunch also rose just as instantly and dramatically. For real unpleasantness being sick into an oxygen mask takes a lot of beating. 
Fortunately I didn't have to endure it for long .... I passed out and have no memory of the remaining ten minutes or so until I was being hauled out the cockpit by a grinning ground crew. 
Cut me down to size in one short lesson. Especially when the significance of money changing hands revealed itself as bets as to how long I would last. However, the final humiliation was still awaiting. When I passed out my camera was left switched on and left suspended in its safety harness pointing downwards. When we watched the footage a few days later in the projection theatre we were all treated to several minutes of my twitching vomit stained legs as the plane flew though the rest of its routine. 
Thus is the sad and illuminating tale of my first ever flight.  _________________ The subtlety and conviction of any Photoshop effect is invariably inversely proportional to the number of knobs on it ....... |
Posted on 16/10/14 2:22:14 PM |
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GKB
Magical Montagist Posts: 3953 Reply |
Re: Spinning propellers and things
Well that was a baptism of fire for your first ever flight! I never got to fly the Gnat; I did fly the Hawk but not with the Reds. The Gnat was such a small aircraft that it was less an aircraft that you climbed into and more like one that you just strapped on! Flying a fast jet just has to be some of the best fun anyone can ever have - but do get some time in in some aircraft of a lower performance first 
If it's any consolation the 'back-seater' in a two-seat fast jet usually carries a couple of bags with him ... just in case _________________ You're never too old to learn something stupid. |
Posted on 16/10/14 6:32:27 PM |
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GKB
Magical Montagist Posts: 3953 Reply |
Re: Spinning propellers and things
I forgot to mention that the DH88 Comet flew again for the first time in 12 years on 1st August from Old Warden; just a few days short of the start of the England - Australia race 80 years ago. Go along next summer for an excellent day's flying with some historical aircraft. _________________ It only seems impossible. |
Posted on 17/10/14 11:02:28 AM |
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DavidMac
Director of Photoshop Posts: 5472 Reply |
Re: Spinning propellers and things
Yes. Well of course in this case the back seater was the pilot. I had the front seat for clear forward vision for photography. _________________ The subtlety and conviction of any Photoshop effect is invariably inversely proportional to the number of knobs on it ....... |