What are Octaves and Sub levels in KAZE and AKAZE?

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I am having a hard time trying to understand the Octaves and Sub-levels in the Non-Linear Scale space (KAZE and AKAZE). For the SIFT- Octaves is a collection of same sized images and sub-level is number of gaussian blurred images to be generated in the octave. How can this be explained in KAZE and AKAZE? I want to tune the parameters and so need to understand this properly.