Center/Surround (C/S) response is the first step in human vision, which represents many aspects of visual perception. The C/S model has hinted to sharpness, lightness, and contrast improvements in image processing. Retinex is a root of C/S based vision model which restores an intrinsic reflectance image by removing the spatial non-uniformities of illumination. To recreate a viewer's sensation of real scenes, Tone Mapping Operators (TMO) have been actively developed during the past decade in two ways of Spatially-invariant and Spatially-variant approaches and now the latter is becoming major stream. However, since most of spatially-variant TMO are designed independent of input/output Tone Reproduction Curve (TRC) and based on “pixel-based” C/S process, they meets a difficulty in keeping the output local contrast as same as the input image.This paper proposes an improved spatially-variant TMO based on an “area-based” C/S process different from “pixel-based” C/S process that maintains local visual Contrast based on Weber Fraction criterion under the given system TRC. The paper describes a basic mathematical formula and introduces experimental results applied to natural images.