My question is about the difference between single scale and multi scale in scale space theory. But I think I have to write what I understand about scale space theory and what I guess is the difference between single scale and multi scale:

• Kernel is an operator which we put on detected data and save its result as a sample point.
• Out put of operation depends on size of kernel and its coefficients.
• If size of kernel and its coefficients only depend to one independent variable, the operator is single scale, for example for Single Scale Retinex which those only depend on size Gaussian kernel.
• Multi Scale Retinex is a multi scale operator; because it is defined as the weighted average of n Single Scale Retinex images for different σ values.

Am I understand concepts true? Also what about difference between single scale and multi scale?