Here is the original image before processing. You can barely see the distortion and CA of the lens. Here are the steps I took to post process this photo: 1. Two raw conversions were made, one shown here on the right and another darker version. Layer mask was used in PhotoShop to pick the darker version of the sky, the dark parts of the banners, the reflections of the gondola and the bell tower. 2. The combined (flattened) image was then put through PT Lens to correct for barrel distortion and CA. Should I process each of the 2 layers separately through PT Lens and then combine them? The second method might have corrected CA better. 3. Perspective is corrected in PhotoShop. I could have used PT Lens to correct distortion and perspective in one step, but I prefer to use PS so that I can see the result in full screen. I purposely left the vertical lines slightly converging. Otherwise, they look faked to me. 4. I increase the local contrast of the reflections and the lion atop the column with large radius USM. 5. Architectural details were enhanced with small radius (0.3) USM. 6. The full size version was saved, then downsized and sharpened for web upload.