Whether you shoot with a DSLR, a mirrorless camera or even a smartphone in manual mode, three settings govern the brightness of an image: aperture, shutter speed and ISO sensitivity. Together they are called the “exposure triangle”. Understanding them means moving from automatic mode to creative control.
1. Aperture (f/)
Aperture is the size of the lens diaphragm. It is expressed as “f/”: f/1.8, f/4, f/8, f/16…
- Wide aperture (small number, f/1.8): lots of light, very blurred background. Ideal for a portrait.
- Small aperture (large number, f/11): less light, everything sharp from near to far. Ideal for a landscape.
2. Shutter speed
This is the length of time the sensor receives light: 1/1000 s, 1/250 s, 1/30 s, 1 s…
- Fast speed (1/1000 s): freezes movement (a running child, sport, a bird in flight).
- Slow speed (1/15 s and below): creates motion blur (silky water, light trails) but needs a tripod.
A useful rule: to avoid camera shake when handholding, keep a speed at least equal to the inverse of the focal length (1/50 s for a 50 mm lens).
3. ISO sensitivity
ISO amplifies the sensor signal. At low ISO (100–200) the image is clean; at high ISO (3200 and above) it becomes brighter but may show noise (grain). Raise it last, when aperture and speed are no longer enough.
How do you combine them?
Each setting compensates for the others: opening the aperture allows a faster speed, raising the ISO lets you gain speed, and so on. To start, use aperture priority mode (A or Av) for a portrait, and shutter priority mode (S or Tv) for action.
An example under the New Caledonian sun
At midday the light is intense: low ISO (100), a small aperture or a fast speed to avoid overexposure. In the shade or indoors, open up more and raise the ISO. To understand light better, read my article on golden hour and light in Nouméa.
Read also: photo composition rules · taking better photos yourself.
To organise your session in Nouméa or elsewhere in New Caledonia, contact me: I will reply quickly.
