Luminosidade Relativa Lentes
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
N²
About this calculator
The Lens Relativity Illuminance Calculator is a useful tool for photographers and photography enthusiasts. It helps to calculate the relative illuminance of a lens compared to a standard lens (usually a 50mm f/1.4 lens).
The basic formula to calculate relative illuminance is N², where N is the focal length of the lens. For example, if you have a 100mm f/2 lens, the relative illuminance would be (100/50)² = 4 times lower than the standard lens.
This calculator is useful when you are comparing different lenses for a photo shoot or when you are looking for lenses that are more suitable for certain lighting conditions.
Frequently asked questions
Why is relative illuminance important?
Relative illuminance is important because it affects the amount of light that enters the camera, which in turn affects the quality of the image. Lenses with lower relative illuminance may produce more diffuse or noisy images.
When should I use this calculator?
Use this calculator when you are looking for lenses that are more suitable for certain lighting conditions or when you are comparing different lenses for a photo shoot.
What is the focal length of the lens?
The focal length of the lens is the length of the lens closest to the camera. It is expressed in millimeters (mm).
Why is the formula N²?
The formula is N² because the illuminance of the lens decreases with the square of the focal length. This means that lenses with a longer focal length will have lower relative illuminance.