I have canon EOS 600D and also I have following lenses:

  1. 18-55mm
  2. 55-250mm
  3. 40mm f/2.8

How do I select correct exposure.

what is the sequence of priory.

currently I first changing the iso, aperture and finally I change the shutter speed.

this is correct sequence or not?

please let me know if it is wrong.

  • 8
    There's no correct sequence, neither is there a correct exposure, it all depends on what you're trying to achieve.
    – Matt Grum
    Dec 24, 2013 at 9:17
  • 1
    1) on the exposure dials 2) depends if you set Av or Tv 3) in most cases yes. unless you want to do ugly milky water falls or use longer shutters as a cool way to capture movements. Dec 24, 2013 at 10:33
  • 1
    However, you might have to go back and increase your ISO after seeing your shutter will have to be too slow to avoid motion blur. Dec 24, 2013 at 10:39
  • To big a question for one answer. Exposure rests on those 3 legs and lots of different correct answers possible. If you don't know how to choose the "length" of the legs and want to... Do a basic photography exposure class, read book or search good online resources. If not use auto mode. Better to get a shot than procrastinate over the exposure.
    – Joop
    Dec 24, 2013 at 11:43

2 Answers 2


What I do 60-70% of the time (summary):

Priority 1: Compose the image in my mind.

2: Think 'What do I want in focus, what do I want out of focus? What lens/focal length am I using?'. This drives my Aperture value.

3: 'Do I have a tripod or something still to rest the camera on?' If not don't set the shutter speed to be longer than 1/X (where X is my focal length). 'Is what I am photographing moving? how fast? do I want to show that or freeze the action?' this drives the shutter speed.

4: Adjust the ISO to value which gives the correct exposure.

The other 30-40% I use 'Aperture Priority (A)' or 'Shutter Speed Priority (S)' modes depending on the circumstances.

  • NOTE: I am a novice who is still learning but this process seems to be working for me.
    – MarkP
    Dec 24, 2013 at 14:35

As @Matt Grum says in his comment:

There's no correct sequence, neither is there a correct exposure, it all depends on what you're trying to achieve

For example if you want to achieve great DOF, then you want to lock down your aperture and play with ISO and shutter speed, now whether you change the shutter speed first vs ISO first depends on the situation, if you are shooting a still subject and you've a tripod (landscape for example), then you could lower the shutter speed. if you are shooting a portrait, then probably you'll try to play with the ISO first because people can't stand still for long time and if you have long shutter speed you'll get a movement.

Same goes if you're trying to get a specific shutter speed in mind, maybe freezing water drops or shoot long exposure shot of a waterfall for example.

Bottom line is, there's no priority, it's just about the effect that you want in mind, this will drive your settings to achieve the exposure you want

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