ISO and image noise

In short: The ISO value indicates how sensitive the sensor is to light. High ISO (3200) allows shots in low light but produces more image noise.

In more detail: Doubling the ISO value corresponds to one stop more light. Noise arises from amplifying a weak signal.

In detail

• Typical values: ISO 100–200 in sun, 800–1600 indoors, 3200 and more at night.
• Sensor size: Large sensors (full frame) are less noisy than small ones (smartphone) (sensorgroesse-und-bildqualitaet).
• Auto ISO: Practical when you want to fix aperture and time.
• Noise reduction: Software can reduce noise but costs detail. With RAW you have more room.
• Use light sources: Better more light (window, flash) than high ISO.
• Trade-off: A slightly noisy, sharp photo beats a clean but blurred one (blende-und-schaerfentiefe, verschlusszeit-und-bewegung).