Photography is the art and science of recording light. Every photo depends on how much light reaches the sensor, where the light comes from, and what color that light contains. Learning to control light helps you make sharper portraits, brighter action shots, moodier landscapes, and more expressive creative projects.
The same physics ideas used in optics, color, and waves also show up every time you press the shutter.
Key Facts
- Exposure is controlled mainly by aperture, shutter speed, and ISO.
- A lower f-number, such as f/2, means a wider aperture and more light entering the camera.
- Doubling the shutter time, such as 1/250 s to 1/125 s, doubles the light collected.
- Illuminance follows an inverse square pattern: light intensity is proportional to 1/d^2.
- White balance adjusts color temperature, measured in kelvins, so whites look neutral.
- A photon has energy E = hf, where h is Planck's constant and f is light frequency.
Vocabulary
- Exposure
- Exposure is the total amount of light captured by a camera sensor or film during a photo.
- Aperture
- Aperture is the adjustable opening in a lens that controls how much light enters the camera.
- Shutter speed
- Shutter speed is the length of time the sensor is exposed to light.
- ISO
- ISO is a camera setting that controls how strongly the sensor signal is amplified, making an image look brighter or darker.
- White balance
- White balance is a setting that corrects color shifts caused by different light sources.
Common Mistakes to Avoid
- Using only ISO to brighten a dark photo is a mistake because high ISO can add visible noise and reduce detail. Try adjusting aperture, shutter speed, or lighting first when possible.
- Choosing a slow shutter speed for moving subjects is a mistake because motion can blur across the sensor during the exposure. Use a faster shutter speed for sports, pets, or handheld shots.
- Ignoring the direction of light is a mistake because front, side, and back lighting create very different shadows and moods. Move the subject or camera to control shape and contrast.
- Mixing indoor bulbs and daylight without checking white balance is a mistake because different color temperatures can make skin, paper, or clothing look unnatural. Set white balance or use one main type of light.
Practice Questions
- 1 A photo is taken at 1/500 s. If you change the shutter speed to 1/125 s and keep aperture and ISO the same, how many times more light reaches the sensor?
- 2 A lamp is 1 m from a subject. If the lamp is moved to 2 m away, what fraction of the original light intensity reaches the subject, assuming inverse square behavior?
- 3 You want to photograph a friend near a window with soft shadows and natural skin color. Explain where you might place the friend, the camera, and the light source, and which camera settings you would think about first.