This article presents a novel parametric model to include expressive chromatic aberrations in defocus blur rendering and its effective implementation using the accumulation buffering. Our model modifies the thin-lens model to adopt the axial and lateral chromatic aberrations, which allows us to easily extend them with nonlinear and artistic appearances beyond physical limits. For the dispersion to be continuous, we employ a novel unified 3D sampling scheme, involving both the lens and spectrum. We further propose a spectral equalizer to emphasize particular dispersion ranges. As a consequence, our approach enables more intuitive and explicit control of chromatic aberrations, unlike the previous physically-based rendering methods.