An image processing apparatus configured to generate a wide dynamic range, WDR image, comprising: an image sensor configured to output a WDR unit comprising a sequence of a predetermined number of image channels, each channel corresponding to a sub-image obtained under variable exposure time; at least one processor configured to implement: a mode setting unit which changes a photographing mode from a first mode in which a first number of sub-images of the WDR unit are synthesized to a second mode in which a second number of sub-images of the WDR unit are synthesized, based on luminance of the output image data, the first number and the second number being different; and a register setting unit which changes a register value of the image sensor according to the second mode, wherein the register value comprises a maximum exposure time (Vmax) and an exposure time (VL, L, S, VS) for each image channel according to the second mode; and an image signal processor, ISP, configured to generate a wide dynamic range image by synthesizing the second number of sub-images from a WDR unit obtained according to the changed register value, wherein the maximum exposure time is set in inverse proportion to a number of sub-images to be synthesized for generating the wide dynamic range image, characterized in that the predetermined number of image channels in a WDR unit output from the image sensor and received by the ISP is constant regardless of the photographing mode being the first mode or the second mode. an image sensor configured to output a WDR unit comprising a sequence of a predetermined number of image channels, each channel corresponding to a sub-image obtained under variable exposure time; at least one processor configured to implement: a mode setting unit which changes a photographing mode from a first mode in which a first number of sub-images of the WDR unit are synthesized to a second mode in which a second number of sub-images of the WDR unit are synthesized, based on luminance of the output image data, the first number and the second number being different; and a register setting unit which changes a register value of the image sensor according to the second mode, wherein the register value comprises a maximum exposure time (Vmax) and an exposure time (VL, L, S, VS) for each image channel according to the second mode; and a mode setting unit which changes a photographing mode from a first mode in which a first number of sub-images of the WDR unit are synthesized to a second mode in which a second number of sub-images of the WDR unit are synthesized, based on luminance of the output image data, the first number and the second number being different; and a register setting unit which changes a register value of the image sensor according to the second mode, wherein the register value comprises a maximum exposure time (Vmax) and an exposure time (VL, L, S, VS) for each image channel according to the second mode; and an image signal processor, ISP, configured to generate a wide dynamic range image by synthesizing the second number of sub-images from a WDR unit obtained according to the changed register value, wherein the maximum exposure time is set in inverse proportion to a number of sub-images to be synthesized for generating the wide dynamic range image, characterized in that the predetermined number of image channels in a WDR unit output from the image sensor and received by the ISP is constant regardless of the photographing mode being the first mode or the second mode.