TERMIUM Plus®

The Government of Canada’s terminology and linguistic data bank.

FOCAL RATIO [5 records]

Record 1 2002-09-06

English

Subject field(s)
  • Optics
  • Photography
DEF

The apparent relation between the shape, visual scale and position of visible objects ...

OBS

The size of identical objects at different distances from the observer appear to be in inverse ratio to their distances. In viewing a photograph, the eye receives the same perspective impression as it would when viewing the original scene if a contact print of the photograph is viewed at a distance equal to the focal length of the camera lens used.

French

Domaine(s)
  • Optique
  • Photographie
DEF

Qualité perceptuelle de la troisième dimension dans l'espace ou sur une représentation graphique plane, comme un dessin.

Spanish

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Record 2 2002-03-01

English

Subject field(s)
  • Remote Sensing
CONT

Vegetation monitoring has been one of the main focal points of remote sensing study since remote sensing research began. Many vegetation indices, using red and infrared reflectance, have been devised. The Perpendicular Vegetation Index(PVI), Ratio Index and Normalized Vegetation Index are among the well known indices of this type. The Perpendicular Vegetation Index, proposed by Richardson and Wiegand(1977), was defined as the distance from the soil line on a scatter plot of near infrared(NIR) versus red reflectance. The pixel vectors of bare land in such plots vary with soil moisture content. The PVI was developed as a vegetation index to effectively monitor the vegetation biomass without being affected by differences in soil background.

OBS

perpendicular vegetation index; PVI: term and abbreviation officially approved by the RADARSAT-2 Terminology Approval Group (RTAG).

French

Domaine(s)
  • Télédétection
DEF

Indice de végétation utilisé pour la surveillance de la biomasse sans que n'entrent en compte les différences de l'arrière-plan sol.

OBS

indice de végétation perpendiculaire; PVI : terme et abréviation uniformisés par le Groupe de travail de la terminologie de RADARSAT-2 (GTTR).

Spanish

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Record 3 1999-03-24

English

Subject field(s)
  • Photography
  • Optics
  • Optical Instruments
DEF

The ratio of the focal length of a lens to the diameter of the effective aperture-the so called f number.

French

Domaine(s)
  • Photographie
  • Optique
  • Instruments d'optique
DEF

Diamètre utile d'un objectif ou d'une lentille par lequel passe la lumière.

OBS

On le calcule en déterminant le rapport entre le diamètre du diaphragme et la longueur focale de l'objectif.

Spanish

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Record 4 1976-06-19

English

Subject field(s)
  • Optics

French

Domaine(s)
  • Optique

Spanish

Save record 4

Record 5 1976-06-19

English

Subject field(s)
  • Optics

French

Domaine(s)
  • Optique

Spanish

Save record 5

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