So, I've been thinking about getting an extension tube for my Bronica ETR, and I was just curious which one people find most useful? Mainly I'm thinking I would use it on the 150mm for portraits to have a little wiggle room to get a bit closer to the subject, but possibly some light macro work too. I already have a 1:1 macro setup in 35mm, so I don't plan on doing pictures of insects or anything. Of the 14, 28, and 42 it seems like the 28 might be the sweet spot, but i'm not entirely sure how much closer it would allow me to get, or what kind of exposure compensation to expect with any of them. Thanks.