Monday, February 11, 2008

Aerial gymnastics

Just after dawn this morning I heard a familiar sound. A fairly loud, fairly frequent "whoosh", echoing off the walls of the nearby buildings. We hear it a bit down my way, more often between March and September. Hot air balloons. They usually fly in the early mornings when the air is cooler so that the hot air that provides the lift is more effective.

It seems that the prevailing breezes push them down the river, and the pilots are quite skilled at keeping them just high enough to avoid trouble, and yet low enough to give their passengers a great view of the city. The "whooshing" noise comes from the gas burner which heats the air in the balloon. The air wants to cool and contract, which doesn't make for long and happy flights, so the pilot has to heat the air in the balloon to keep it afloat. They are masters of elevation, but direction isn't totally in their control!

Still, it looks like great fun. The one time I tried it, I was amazed at how quiet it is, and how close to the ground you really are.

In terms of matters photographic, I used the spot metering function of my camera to ensure that the balloon itself was properly exposed. I waited for the flame from the burner to be visible before pressing the shutter, because it gives the images more impact. The VR function of my lens was invaluable, because even though I was using 400 ISO, the shutter speeds were still rather low. In truth, I made a slight error in the rush to get my equipment ready quickly - I selected an aperture of f8; slightly too much for this shot where DOF isn't important. If I had selected f4 then I would have had more manageable shutter speeds for hand-holding the telephoto lens.

EXIF: Nikon D200; Nikkor 80-400 mm VR; ISO 400; 1/80 sec (1), 1/50 sec (2).

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