Face recognition has attracted significant attention due to its wide range of
applications. Recently, researchers have focused on robust face recognition such as
face recognition systems invariant to pose, expression and illumination variations.
Illumination variation is still a challenging problem in the face recognition research
area, especially for appearance-based approaches. This paper will discuss two main
categories of the existing illumination methods namely frequency domain approach
(DCT & DWT) and filtering approach. This includes the introduction of the
representative algorithms, theories, and analyze the advantages and disadvantages of
these algorithms correspondingly. The aim of this paper is to explore the technique
and limitations of the existing illumination normalization strategies. Based on the
reviews that have been conducted, it is found that the filtering technique is more
effective when compared to the frequency domain technique. Hence, the implications
of the review can help researchers to propose a novel idea in order to solve the existing
problems and automatically improve the recognition performance.