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I am new to photography but have a fairly good understanding of exposure.
I know the camera's light meters are easily fooled and hence the need for exposure compensation where a photographer have the ability to manually over/under compensate to obtain a "correct" exposure.
Assuming you have (and know how to use) a good light meter (Sekonic etc.), does this mean you will never need to use the exposure button on your camera to obtain a correct exposure?
Yes and no.
If you are using a light meter, then you will never use the exposure compensation because you are setting the exposure manually.
However, just because you measure the incoming light instead of the reflected light, that doesn't mean that every scene can be exposed only based on what the meter says.
Instead of being fooled by how much light the subject reflects, the light meter completely ignores it, and thus you may be fooled in a different way. As different subjects reflect light in different ways, you may need to adjust the exposure accordingly.
your external meter wont tell you if your scene should be or not be medium exposed. that's what EC is for. if you shoot at a white wall, everything should be close to max. you make that decision how to use the value you get from the meter. just like the EC feature allows you to. often the Dynamic range in the scene is too large and you can point your meter to different parts, but you still have to make compensation in your mind when setting the exposure from those number based on your own choice, if you want to focus on the highs or lows, or so the medium setting that the value is good at picking. I have to use EC for a different reason, when I push my camera capabilities in very low light. if I dont go for EC -1 or 2 , the shutter time will be too large giving me motion blur. This situation may not be applicable if you have some for hte external metering.
It depends what you're using exposure compensation for. If it's because your camera's built-in meter sometimes gets somewhat inaccurate in certain situations (e.g. Pentax cameras tend to under-expose slightly) then yes, a good quality external light meter would obviate the need for exposure compensation (though, as Guffa says, in order to use the external light meter's findings you need to be in M mode which doesn't have exposure compensation!).
If on the other hand you're using exposure compensation because you want a less-than-scientifically-perfect exposure (e.g. you want to underexpose to make the resulting image more 'moody') then a light meter won't really make any difference (other than allowing - or rather forcing - you to do it more precisely in Manual mode)
