1. A dynamic exposure adjusting method adapted for an electronic apparatus, comprising: capturing a plurality of preview images, a plurality of additional images, and a first image, wherein the additional images are not displayed in a display unit of the electronic apparatus; dividing the first image into a plurality of blocks; analyzing a luminance distribution condition of the first image, wherein the analyzing includes counting a first number of bright blocks above a predetermined luminance threshold and a second number of dark blocks below said predetermined luminance threshold; obtaining a long exposure time and a short exposure time according to the luminance distribution condition of the first image at least by, wherein the obtaining includes calculating a ratio value between the first number and the second number and obtaining the long exposure time and the short exposure time according to the ratio value; selecting and retrieving at least one specific image corresponding to the long exposure time and the short exposure time from the captured additional images; and combining the first image and the at least one specific image as one processed image.