Q : I got a dark image – I dialled in an exposure compensation of +1, +2, +3 — Still it came out dark
To understand why your camera is doing something not quite how you want it (I won’t call it wrong), it is essential to understand how your camera works. So for e.g. in the above case, if you have a scenario where you got a dark image and you dialled in an exposure compensation of +1,2,3 etc. it should give you brighter images right? I mean logically speaking, when you tell the camera to over-expose (+1 +2 etc), you are basically telling the camera to allow more light and thus get a brighter image right?
Well the actual result depends on what your settings were to start with.
Assume that you were in Tv/S mode – under which case you would be controlling the Shutter and the camera controls the aperture, right?
Now further assume that the aperture value is f/3.5 (which also happens to be the widest in your lens) to start with. Now, if you dial in an exp. compensation +1, there is no way the camera can open up the aperture wider. It wouldn’t be able to even if it wanted to because the limit of the aperture of your lens is f/3.5.
What the camera will do, is that it will start blinking the aperture, trying to tell you that it is not able to do what you want it to.
Note that your camera always tries to help you. Notice the blinking and act accordingly. In this case for example I will try and control the ISO, bump it up and make the camera more sensitive to light and then see the difference.