You are not quite correct. The deconvolution only works well if you know exactly the convolution kernel and you have infinite signal to noise. In practice neither is true and you'll have artefacts if you try to do deconvolve. And the reason why it's hard to know exactly the convolution kernel is that it will depend on the wavelength of the photons, position in the focal plane and potentially orientation of the camera, if optical elements are moving around.