Patent ID: 7453496

Claim:
An image composition method comprising: composing a high-sensitivity image signal H and a low-sensitivity image signal L, so as to generate a composite image signal Gc according to a composing expression: Gc=k·H +(1− k )· L where k is a composite parameter satisfying 0≦k≦1, wherein the high-sensitivity image signal H is generated based on high-sensitivity image outputs from corresponding ones of a plurality of pixel positions in a solid-state imaging element that has imaged a subject; the low-sensitivity image signal L is generated based on low-sensitivity image outputs from corresponding ones of the plurality of pixel positions in the solid-state imaging element; the composing is performed at every common pixel position by determining k at every common pixel position; wherein the high-sensitivity image signal H is a signal G H (D H ) obtained by converting a high-sensitivity image signal D H with a nonlinear characteristic G H for a high-sensitivity image signal, the high-sensitivity image signal D H being generated based on the high-sensitivity image outputs; and the low-sensitivity image signal L is a signal G L (D L ) obtained by converting a low-sensitivity image signal D L with a nonlinear characteristic G L for a low-sensitivity image signal, the low-sensitivity image signal D L being generated based on the low-sensitivity image outputs; and wherein the nonlinear characteristic G H for the high-sensitivity signal and the nonlinear characteristic G L for the low-sensitivity signal have a characteristic of realizing a monotonously-increasing function, whose change in a secondary differential value is positive or zero at all times.