Log is the manner of capture of choice for lots of videographers, as it gives a lot more dynamic range and creative freedom, though it takes more work in post-processing. This excellent video will show you how to grade Canon Log footage (though the lessons can apply to any brand).
Coming to you from Bryan Redding of the Deaf Director, this fantastic video tutorial will show you how to grade Canon Log footage. Log is so named because it refers to a logarithmic function, which in turn refers to the tonal response curve of the mode, which allows for much more dynamic range to be captured — up to 800% more in Canon's case, allowing for a ton more detail to be captured in both the highlights and the shadows. The drawback (or advantage, depending on how you look at it) is that the footage it outputs looks very flat and unsaturated, requiring you to do more work in post. This is really an advantage, however, as it means things like contrast levels and color toning are not baked into the file as it comes out of the camera, leaving you far more creative freedom to adjust things as needed and to add your personal style. Once you get used to working with log footage, you will likely never switch back. Check out the video above for the full rundown from Redding.