Planning a trip abroad and looking for specific lens advice please. Using a Canon 6D and currently have the 24-105mm f4L and 50mm f1.8. Will be doing a night (city) photography tour and also a daytime photo tour. Plan on using the 24 for daytime shooting. Researching a new lens to add to my bag for the night tour and to start doing more night shooting in general. The Canon 16-35 f2.8 (III) and the 20mm both seem interesting. Open to all recommendations though. Any advice on which lens to add for night and low light photography is greatly appreciated.