Ah yes, theres the rub... Not willing to spend much on a (for most of the time) unnecessary (for me) lens ( I dont do portaits). So it would at best get used once every two years for a few days, at this exhibition. So around $150.00 for the basic nifty fifty is all it needs thrown at it at this time. Put it on full frame (5D Mk2) and as you say there may be some instances where it will be a bit tight. Put it on APS-C (1100D) and it does get tight, so would go for some other wider prime. But that starts to increase the budget for something I wont use much...). Leaving me with the 50mm on full frame as a nice compromise OR, forget it entirely and take the 24 to 70 zoom and not worry about the weight factor.... 🙂 Actually that will work. Use the 50mm on full frame at exhibition, and take the 24-105 F4 as my usual travel lens for sight seeing outside of exhibition. Leave 24-70 at home this time.... decisions, decisions.... No?