Merging multiple exposures to generate a high dynamic range image

A system comprising:

• an image sensor configurable to output a first signal having first pixel values of a long exposure image of a scene and a second signal having second pixel values of a short exposure image of the scene;
• and
• an image signal processing circuit coupled to the image sensor to receive the first signal and the second signal,
• wherein the image signal processing circuit is operable to:
• determine a first per-pixel weight based on a difference of luminance of a pixel of the long exposure image and a corresponding pixel of the short exposure image, wherein the first per-pixel weight is not a block-based weight;
• and
• generate a high dynamic range (HDR) image of n-bit data by merging the first pixel values with the first per-pixel weight and the second pixel values with a second per-pixel weight, and
• wherein the image signal processing circuit is further operable to convert the HDR image of n-bit data to an HDR image of m-bit data with performing tone mapping by using a look-up table, wherein m is smaller than n.