For SLR equivalent to 80mm, use 80 / 1.4,which is about 57.

For SLR equivalent to 100mm, use 100 / 1.4, which is about 71.

For SLR equivalent to 150mm, use 150 /1 .4, which is about 107.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)