1. A method for adjusting weighting values in light metering, comprising: dividing an input image into multiple metering zones, the input image including a plurality of pixel data and the metering zones corresponding to a plurality of exposure weighting values; determining whether color of each pixel datum of the input image is skin color; determining the color of each pixel datum which is determined to be skin color again according to a determination result of the pixel datum and determination results of a plurality of neighboring pixel data, wherein if the pixel datum and its neighboring pixel data are all determined as skin color pixels, confirming that the pixel datum is a skin color pixel and if at least one of the pixel datum and its neighboring pixel data is determined as not skin color pixels, confirming that the pixel datum is not a skin color pixel; calculating an amount of the pixel data determined as the skin color for each metering zone; and adjusting the corresponding exposure weighting values of the metering zones according to the calculated results, wherein the step of determining whether the color of each pixel datum of the input image is skin color comprises for a piece of pixel datum, calculating a first reference value and a second reference value according to ratios among a plurality of sub-pixel data of the pixel datum; and determining whether the first reference value and the second reference value are within a predetermined region, wherein the first reference value and the second reference value are calculated as follows: the ⁢ ⁢ first ⁢ ⁢ reference ⁢ ⁢ value = ( R input G input ) 2 + ( R input B input ) 2 - 1.4 the ⁢ ⁢ second ⁢ ⁢ reference ⁢ = tan - 1 ⁡ ( ( R input B input ) / ( R input G input ) ) - 0.7 R input , G input , B input indicate three sub-pixel data of the piece of pixel datum, respectively.