Calculateur de Distance Focale Gratuit
Calculez la distance focale d'une lentille ou d'un miroir. Déterminez le point focal à partir du rayon de courbure.
Distance focale
10.00 cm
Focal Length vs Object Distance
Formule
Focal Length
The focal length defines the converging or diverging power of a lens or mirror.
Formula
1/f = 1/d_o + 1/d_i
Lens power in diopters is D = 1/f (with f in meters). Positive focal length = converging lens; negative = diverging.
Exemple Résolu
An object at 30 cm produces an image at 15 cm.
- 011/f = 1/do + 1/di
- 021/f = 1/30 + 1/15
- 031/f = 0.0333 + 0.0667 = 0.1
- 04f = 10 cm
- 05Power = 100/10 = 10 diopters
Questions Fréquentes
What are diopters?
The unit of lens power, equal to 1/f where f is in meters. Eyeglass prescriptions use diopters. Positive = farsighted correction; negative = nearsighted.
How does focal length relate to camera zoom?
Longer focal length gives higher magnification and a narrower field of view (telephoto). Shorter focal length gives a wider field of view (wide-angle).
What determines the focal length of a lens?
The curvature of the lens surfaces and the refractive index of the glass. The lensmaker's equation relates these to focal length.
Apprendre