Digital 3D 'bins' have a place, but will twitchers be switchers?

A greenfinch looks on suspiciously from afar. The finest details of his green and yellow plumage and his eyes twitching from side to side are visible through the binoculars.

He appears to briefly sum up the curious contraption being pointed in his direction. But his interest quickly wanes; he has probably seen thousands of people pointing binoculars at him from this very hide.

Fellow twitchers display a similar lack of interest in the "bins", whose only distinguishing feature seems to be that they are "a bit big for bird watching". But what neither they nor Mr Greenfinch know is that he is being filmed in 3D on the world's first pair of video-recording binoculars.

And while the ornithologists at the RSPB's Bird Fair in Lincolnshire – where the device was unveiled last week – may be content to use them for spying on a rare sighting, others may choose to put Sony's new invention to slightly more nefarious uses.

Only the most vigilant cinema usher or concert steward would have much cause to suspect that these seemingly humble binoculars (albeit costing £2,000) could be used to surreptitiously record copyrighted material in 3D as well as any high-end digital camcorder.

Sony, however, is aiming its newest product squarely at the nature enthusiast market, which a spokesman said has "seen huge growth" in recent years. But will the twitchers of Britain be persuaded to give up their traditional optical binoculars in favour of the new-fangled video version? In a world where the "bird count" – the number of individual species spotted – is the badge of honour, some are reluctant to leave behind the equipment which has served them well thus far. Others, of course, are hunting the next piece of equipment to help them in their quest for birds.

"They are quite heavy, perhaps too heavy to have out all day. But if the quality of the image is high, there will be people out there who will want them," said one twitcher, Michael Hopton, a 67-year-old retired biochemist (bird count: 420). "You might have to be a lottery winner to afford them but I am sure people will be using them before too long. You could use them for other things too, like the races or perhaps a concert."

Fred Johnson, a 56-year-old engineer (bird count: 800), said: "They are quite complex. I'm not sure I would like to have them out in the field with me; they look like they'd not be much good if you dropped them."

He added: "It is hard to see what you would use them for. If I wanted to catch a bird in flight, the video might be good for that but they are quite expensive."

The binoculars go on sale in November and there are currently only three prototypes in the UK. The manufacturer stressed that they are still in the final stages of development.

Disappointingly, there is no "figure of eight" binocular effect when the video is played back. Although, presumably, those who mix their twitching with a love of James Bond films can add that in during post production.

Another twitcher at the Bird Fair, 77-year-old Peter Carlton (bird count: 5,000), said the binoculars would be a "development for the future, certainly" but they were "going to be good". "People will take it up because they can film something they don't know and perhaps identify it later when they watch it back."

After trying them out myself (bird count: 5), I would advise that the same is not wise when applied to people. Pointing them at strangers across the street is considered antisocial, be they simple, old-fashioned opticals or the world's first pair of video-recording electronic binoculars. You have been warned.