I just bought my first adapter: A Rainboximaging Minolta MD-to-M43. It feels solid and weighs 78 grams (2.7 ounces). I'll be attaching it to my first adapted lens, a Minolta MD 100/2.5 "Plain MD". This was the last of three versions of the 100/2.5 MD. It weighs just 310g (vs. 380 and 390g) and uses 49mm filters (vs. 55mm). Clearly, for an M43 shooter who values light weight, it's important to factor in the adapter weight. Especially for a shooter like me, who will be carrying everything in a belt pouch. Which lens mounts use the lightest adapters? Within a mount--say, MD-to-M43, or L39-to-M43--how much heavier do the heaviest-brand adapters weigh than the lightest? Which brands tend to be the lightest? Most brands claim to be made of aluminum and brass. One or two brands just say "aluminum." I would guess they weigh the least. I can see how I'd want an adapter that's heavy and solidly built if I'm adapting a lens that's over 400g, longer than 100mm, or both. But surely if I'm adapting a 300g lens that's only 63mm long, I can get by with a lighter adapter, provided it's built to precise tolerances. Right?