BTW so far there is a plan to have Blend amount for the denoiser. It will be spinner with 0 to 1 value where 0 is original image without denoising, and 1 is denoised image. So after render is done, you can set it to 0 to undo denoising, or you can blend between original and denoised image to get just the right amount. So every time you finish rendering, Corona will store both original and denoised image, and you can save them individually.
You will be also able to adjust denoiser radius and recalculate denoising after rendering is done, but that won't be in realtime anymore, you will have to wait some second for denoiser to do its magic again.