The demand for "anamorphic lenses" or so-called vintage lenses has shot up in the UK because of the popularity of period dramas such as Downton Abbey and Poldark. The film production industry has been raising millions over the past year in order to finance the purchase of these lenses, according to Investec Asset Finance.

Martin Harries, Investec's head of intermediary sales, said: "Modern technology produces a picture that is too crisp and clear for a period drama. The value of these vintage lenses is going up steeply and they are highly sought after because they give the right feel."

Apart from production companies, camera equipment hire businesses are also making bulk purchases of the special camera lenses that were used for making films more than a decade ago. To ensure that the new historical dramas have an authentic, old-world feel, the lenses are used along with modern digital cameras, according to The Telegraph.

Harries indicated the value of the lenses by saying: "One of the deals that our asset finance intermediary closed last year was a set of £36,000 [€49,130, $52,800] Canon lenses, which were used on the 1980s film Aliens. These are still being used now and will never become obsolete because the effect they give is in such high demand."

Investec Asset Finance reported that the demand had shot up so high that the sector witnessed deal values rise by 1,620%.

Azule Finance, the specialist funding and leasing services firm, which works exclusively with media, film and TV companies, said production companies are investing a lot of money in this kind of lenses because they are anticipating many new period dramas and other series that require a lesser sharp picture, to hit the floor.

Gavin Scott, managing director of Azule, said: "Netflix, Amazon and Sky are all vying to produce the next hit drama and they are filming in the UK to take advantage of the current tax breaks. There is a 12 to 24-month waiting list for new anamorphic lenses so companies are looking for the old ones instead."

While film production companies raised £40m in finance from Azule in 2014, the number increased by £5m in 2015.