I've got two Sigma lenses that take a 77mm cap and both are always loose.
Yesterday I got home and found the lens cap had come off the 70-200 in my bag and with any pressure would have been re-grinding the front element for me . Felt like my guts had turned to jelly and had shivers down my neck when I noticed and was checking for any scratches....
Luckily it was ok and now I have put a cheap UV filter on so that if the cap does come off again the lens will be safe. I don't really want to continue using the UV filter because if it takes a knock im now worried about glass fragments (there was a thread not long ago where this happened to a member here).
Anyway question is does anyone else have this problem with their Sigma caps or is it just me? and are Canon and Tamrons better designed so that they stay on better?