I have been viewing alot of lovely shots with these lenses. They both have great bokeh, for wide angles. the 28mm f2.8 ais has better nonagonal highlights as well as round bokeh. The 20mm f2.8 has better handling of infrared film, vs the hotspot on the 28 f2.8. Please provide some comments and input on these two, as they are both superb and I don't plan to have 2 wides. Can the infrared issue on the 28mm be minimised by stopping down to f4?