dan - i hope that you're feeling better, and your back recovering.
if you're a "50mm shooter", i think that there is little need for you to now replace that with a 35mm just becuase you want to carry less - the shooting styles for the 2 focal lengths can be subtlely yet significantly different. for instance, the 50 is versitile enough to handle portrait, candids, environmental portraits, landscape, etc (your flickr photostream can attest to that)... as can the 35mm, but in a different style.
to min weight, i would suggest just bringing a pair of lenses - e.g. 21-50, 28-50, 35-50, with 1 body, or 2 (1 digital, 1 film). i personally travel with either a 28-50 or a 35-50 pair.
there's no need to preach to the preacher about which 50mm to bring, but for the 35, just bring along what you have for now - fujinon f/2, cv f/1.2, whichever... it is afterall, the alternate lens to your staple 50. if you're looking for a smaller 35mm that need not be kept in a safe deposit box, the 35cronIV or its derivates are good choices (canon v1/v2 and konica chrome/UC). the "dual personality" 35luxpreasph can be another contender. if you want sharp and higher contrast, can try the biogon or asph lenses.
bottomline, what i'm trying to say is don't change from a 50 to a 35 because you want to save your back... you will revert back to the 50 in no time. instead, you must want to see the world through a different view of the 35mm lens... in which case, the conversation and the journey would be a lot more fulfilling and rich!!
while Chiff's is the black version with the silent mode. With the silent mode enabled, you can even hear a pin drop... :thumbsup:
