What do P, A, S and M mean on my camera dial?

The mode dial is not a difficulty scale from easy to expert. It is a list of which decision you are taking off the camera, and the right one depends entirely on which side effect matters in the shot in front of you.

Step by step

1. Read the dial as a division of labour.In every semi-automatic mode you set one exposure control, the camera sets the other to match, and ISO is either fixed by you or floating within a limit you set. Nothing more is happening.
2. Use A or Av as your default.Aperture priority. You choose depth of field — the thing that most changes how a photograph looks — and the camera keeps the exposure correct. It is what most experienced photographers leave the camera on for general use.
3. Switch to S or Tv when movement is the point.Shutter priority. Set 1/500 or faster to freeze people moving, 1/1000 and up for sport, or a slow speed deliberately to blur water or traffic. The camera opens or closes the aperture to compensate.
4. Use M for constant light or awkward meters.Manual is right in a studio, under stage lighting, for panoramas, for astro work and for anything where the meter keeps changing its mind across frames that need to match. It is a tool for consistency, not a badge.
5. Set Auto ISO with a floor and a ceiling.This is what makes semi-automatic modes genuinely usable. Set a minimum shutter speed you can hand-hold and a maximum ISO you are happy with, and the camera manages the third variable within your limits.
6. Know what P actually does.Programme mode picks a sensible aperture and shutter pair, but unlike full auto it leaves you exposure compensation, white balance, flash and file format. On most cameras you can also rotate a dial to shift through equivalent pairs. It is a reasonable mode for walking about.
7. Understand what full Auto takes away.The green mode usually locks exposure compensation, forces the flash up, may force JPEG and often overrides the drive and focus modes. That is why it feels like the camera is fighting you — it is.
8. Watch the number the camera chose.In A mode, glance at the shutter speed it picked. If it has dropped below what you can hand-hold, you have a blur problem coming, and the fix is a wider aperture or a higher ISO limit.
9. Learn the custom slots if your camera has them.C1, C2 and U1 save a complete configuration — mode, ISO limits, focus mode, drive. Setting one up for moving subjects and one for general use means a single turn instead of six menu changes.

Tips

• Aperture priority plus Auto ISO with a minimum shutter speed handles the overwhelming majority of real photography.
• If manual mode feels like a struggle, you are probably using it where the light is changing. Manual suits constant light.
• Scene modes are just presets for these same settings. There is nothing in them you cannot set yourself, and they usually restrict the file format.

Common mistakes

• Treating manual as the goal — Manual is right when the light is constant. In changing light it means every frame has a different, usually wrong, exposure while you catch up. Aperture priority with compensation is both faster and more accurate.
• Using aperture priority without watching the shutter speed — In dim light the camera will happily choose 1/15 of a second to keep the exposure correct, and every frame will be blurred. Set a minimum shutter speed in the Auto ISO settings.

If it doesn't work

Questions people ask