doubler n : an electronic device that doubles the voltage or the frequency of an input signal

English

Noun

1. One who doubles

French

Etymology

From duplare.

Verb

doubler

1. to double, duplicate

   A cet instant précis, il a décidé de doubler la mise.

2. to double-cross

   Nous avons été doublé ce coup-ci.

3. to overtake, pass

   Sur l'autoroute, nous avons eu l'occasion de doubler de nombreux véhicules.

4. to dub

   Daniel Beretta qui double Arnold Schwarzenegger en français depuis 1987 a également prêté sa voix à l'agent Sam Fisher.

Conjugation

Derived terms

• doublage
• redoubler
• dédoubler

A teleconverter is a secondary lens which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens. For example a 2× teleconverter enlarges the central 12×18 mm part of an image to the size of 24×36 mm. Teleconverters are typically made in 1.4×, 2× and 3× models.

The use of a 2× teleconverter (or doubler) gives the effect of using lens with twice the focal length. It also decreases the intensity of the light reaching the film by the factor of 4 (an equivalent of doubling the focal ratio) as well as the resolution (by the factor of 2).