Camera Basics: How a Shot is Made

Aperture

The adjustable opening in the lens, measured in f-stops, controlling light and depth of field.

Shutter Speed

How long each frame is exposed to light; affects brightness and motion blur.

ISO

How sensitive the sensor is to light; higher ISO is brighter but noisier.

Frame Rate

Frames captured per second, e.g. 24fps for a cinematic look.

Depth of Field

How much of the image in front of and behind the subject is in focus.

You are filming a friend indoors and the shot is too dark. Here are your options, in the order a pro would try them.

1. 11. Add light: Open a curtain or add a lamp. Real light always beats fixing it in the camera.
2. 22. Open the aperture: Go from f/5.6 to f/2.8 — four times more light, but the background blurs more.
3. 33. Keep shutter at 1/50: At 24fps, don't slow the shutter past 1/50 or movement smears.
4. 44. Raise ISO last: Push ISO from 400 to 1600 only if the shot is still dark — expect some grain.

pythonframe_rate = 24
shutter = 1 / (frame_rate * 2)   # 1/48 -> use 1/50 on camera

scene_brightness = 30            # arbitrary light meter reading
aperture = 5.6
iso = 400

while scene_brightness < 50:
    if aperture > 1.8:
        aperture = aperture / 1.4    # open one stop
        scene_brightness *= 2
    else:
        iso = iso * 2                # last resort: more grain
        scene_brightness *= 2

print(aperture, iso, shutter)

The planner opens the aperture first and only raises ISO when the lens is wide open — the same order a camera operator works in.