True, but when you have an awful lot of layers, you can play some silly buggers with it. Even if you botch a layer, it won't neccesarily ruin the whole thing, s

True, but when you have an awful lot of layers, you can play some silly buggers with it. Even if you botch a layer, it won't neccesarily ruin the whole thing, since the interference betwen the sets of layers also act as filters. I haven't worked on these sorts of stacks, personally, but I'd be surprised if the whole stack dies because one layer was a bit screwed up (I'd expect a degredation in the efficiency, but not necessarily a total reversal - now ask me what happens if your goal is to tune to neutral color and you make a slight error and then I'll flip sides and say "rainbow"). What I'd really expect is that if you make one layer slightly larger, your process almost certainly making all the repititions of that layer larger too, and now yeah, your bulk properties are just hosed.