Need f-stops explained

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Originally Posted by Colin Southern

It's been said that the aeroplane of the future will have only a single pilot and a dog in the cockpit. The pilot's sole job is to feed the dog. The dog's sole job is to bite the pilot if he touches anything!

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I've been informed that is what it is like now; in fact Air France springs to mind with pilots stalling after disengaging autopilot.

We also have Russian pilots that apply brakes on take off; so maybe all that is needed is blow up pilots just to keep the passengers happy, although they don't frighten easily since they wasn't too bothered when a wheel fell off a FlyBe Dash aircraft.

Won't catch me in one of those things without sedation. :)

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Originally Posted by arith

I've been informed that is what it is like now; in fact Air France springs to mind with pilots stalling after disengaging autopilot.

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Hmmm, perhaps ... I'm waiting for the official report though. From what I've read from other long haul jet jocks there may well be a lot more to it.

If anyone is keen for some good insights into the cockpit of an Airbus, check out flightlevel390.blogspot.com.

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Originally Posted by arith

Won't catch me in one of those things without sedation. :)

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*Doesn't want to know the amount of sedation needed in roadtraffic* :p

Here's a bit of fun; most of all I know is from simulators and it looks a bit harder than square root of 2. Can't see what its got to do with photography and I don't understand the captain.

I thought the Airbus was unsinkable; oh yes I remember reading about the reliability of safety critical systems in the 80's. :)

http://www.myaviationschool.com/free...simulator.html

As long as we are so far off topic that we may never find our way back,

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The dog's sole job is to bite the pilot if he touches anything!

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...

Each year, bush pilots gather in Alaska to compete for Shortest Takeoff and Landing (STOL) distances.
In a competition where less is more, Doyle’s total takeoff AND landing distance was a mere 78 feet.
That’s 43 feet for the takeoff and 35 feet for the landing.

http://freedom4um.com/cgi-bin/readart.cgi?ArtNum=133255

-To get back to the subject of f stops, this is taken from the Focal Encyclopaedia of Photography Desk Edition, 1978 reprint

Relative Aperture: THis is the ratio of the focal length of the lens to the diameter of the effective aperture. For example, if a lens has a focal length of 100mm and the effective aperture has a diameter of 25mm, the relative aperture is 100/25 = 4. This is also known as the f-number and is expressed as f/4,f4, 1:4 etc.
The light passing power of the lens, and hence the exposure required in a photograph, depends on the relative aperture. Lenses of different focal length and different effective apertures still form an image of the same brightness, other things being equal, if the relative aperture or f-number is the same. (in practice light losses by absorption and reflectioncomplicate the situation slightly). In common photographic parlance the term aperture is taken to mean the relative aperture.
The light transmitted through the lens is proportional to the area of the effective aperture and hence inversely proportional to the square of the relative aperture of f-number. In other words a lens set to f4 passes four times the light of a lens set to f-8.