Human eagle eyes

Sound… Camera… Action!” The huge Arriflex Cine camera started to roll while the focus puller fiddled with the controls, the director dived under the black cloth to watch the recorded image on the monitor screen and I released my trained tawny eagle, Veruschka, over the cliff.
Issue date : 20 June 2008

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Sound… Camera… Action!” The huge Arriflex Cine camera started to roll while the focus puller fiddled with the controls, the director dived under the black cloth to watch the recorded image on the monitor screen and I released my trained tawny eagle, Veruschka, over the cliff. The shooting of a new TV commercial for Peugeot-Europe was is full swing.

They wanted eagle flight-shots to merge with those of a car speeding along a winding mountain pass. main film crew was shooting the car-sequences at Baines Kloof, while we were working on a hilltop near Worcester, about 25km away. Directors always want to repeat a shot several times, although with an eagle your first flight is always the best.

After the third repetition Veruschka had enough of senselessly flying around a small hill and headed straight for the foothills of the majestic Hex River Mountains, not far away. Within minutes she caught one of the delightful updrafts and became a minute speck thousands of metres above the peaks. Riding the wind, she soon vanished from sight. Crossing the Breede River, she followed the south-east wind where it funnels through a poort in the Slanghoekberg, towards the rest of the film crew at Baines Kloof. magine their surprise, when literally out of the blue a large brown eagle appeared and soared around them, enabling them to capture on film both car and bird together.

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This perfectly executed choreography of an impossible script made our earlier efforts to get flight shots almost unnecessary. n the meantime, not knowing where Verushka had gone, grew increasingly concerned. No amount of calling or luring with half a rabbit on a thong had any effect. But still had an ace up my sleeve. In the past, whenever couldn’t see her simply drove off on my quadbike pretending to leave her behind and in no time she would be soaring above me.

So, leaving my companions behind me, drove down the hill and took the road to Worcester. But at Baines Kloof something strange was happening. Veruschka suddenly caught a strong updraft and within seconds mounted to an enormous height, then tilted her wings backwards and went into a soaring dive towards Worcester. only drove about 3km and then stopped and threw out the rabbit and waited, but not for long. Within minutes she was there landing on the lure, proving that the experts, who’d have us believe the eyesight of an eagle is eight times keener that ours, haven’t a clue what they’re talking about.

Looking further

Humans, together with other primates, have the best eyesight of all mammals, but it’s no match for birds, eagles in particular. For a human to see, let alone recognise a man on a bike 25km away, takes infinitely more than a mere eight times magnification. It can only be done with an extremely powerful optical device, the first of which was designed and built by a Dutch spectacle maker Hans Lippershey in 1608, exactly 400 years ago. He called it a telescope. he next year the famous astronomer and physicist Galileo Galilei heard about this wonder-device and immediately built his own improved version.

His first telescope had only three times magnification, but within a year he had increased its magnification to 33 times and discovered not only the craters on the moon, but also the spots on the sun, the phases of Venus, the satellites of Jupiter and the rings of Saturn. His telescope consisted of a long tapering tube with a suitable lens on each side. To avoid confusion you have to close one eye when using it. Because Galileo introduced it to astronomers, henceforth it carries his name, the Galilean telescope. It remains the basis of all photographic telephoto lenses.

Designing onward

Soon, however, there was a demand for a binocular telescope that could be used with both eyes, and again it was Lippershey who built the first bulky prototype. However, it took almost a century before a certain Johann Zahn created a double handheld telescope in 1702, which was in fact the world’s first pair of giant binoculars. Although portable, it was very long and quite bulky and still far from the compact little marvels we have today.

For that the world had to wait another 150 years until 1854, when the Italian optician Ignatio Porro fitted two opposing triangular prisms inside each telescope tube to direct the light beams entering the widely spaced objective lenses at the front, along Z-shaped paths to the ocular lenses (or eyepieces) at the rear.

Thus Porro managed to reduce the overall length of his binoculars significantly and the widely spaced objective lenses also gave improved depth perception. For more than a hundred years, the porro prism design remained the standard of all binoculars, compact telescopes and spotting scopes. Then, in the 1960s, Zeiss and Leitz introduced the roof prism binoculars, whose objective lenses were straight in line with the eyepieces. This enabled them to reduce the width of their binoculars to make them even more compact.

Looking more modern than the old-fashioned zig-zag shaped porro prism binoculars, the roof prism binocular became immensely popular and even fashionable. It was light and compact and comfortable to hold, but had one drawback – price. Although appearing simpler than porro prisms, on the inside, the roof prism has a more complex light path, which requires much greater optical precision and therefore costs more to make. In the meantime, telescope development made great strides. In 1668 Sir Isaac Newton had designed a telescope that didn’t work with lenses, but with a dish-shaped mirror that reflected the image to an eyepiece on the side. That same year Laurent Cassegrain improved Newton’s design.

He used a second rearward-facing small mirror in the front of the telescope, which reflected the image back to the eyepiece through a small hole, drilled in the centre of the large main mirror. This is still the principle on which most reflecting telescopes work. The 20th century saw the construction of giant reflecting telescopes, which widened human knowledge of the universe beyond imagination.

Many types of complex telescopes have been developed not only for light waves, but for gamma and radio waves, the first of which went into operation in 1937. Without them, space travel would have remained merely a science fiction dream. Sight is by far the most important sense we have and most people crave to enhance their ability to see. Optical devices to help us achieve this abound, although none can make us see as well as eagles. Besides spectacles, a pair of good binoculars is the field sportsperson’s most valuable visual aid. – Abré J Steyn Contact Abré J Steyn on 083 235 4822 or e-mail [email protected]. |fw