If you think that a GX-7 is good enough for you, stick with it. There is quite a big jump in price to get a GX-8 with its newer sensor technology....
Well, I dug my E-PM1 out and have had a play with it, and it does indeed seem very keen to "up the ISO" to 1600 when light levels fall.
It should be capable of very good results.... I hope there's not a fault with it?
Certainly start off by setting the ISO to 200, I don't know why...
I traded my D80 in a few years ago but the requirement was that the body and lens should both be set to AF "on" for auto-focus to work...
Spewing (the after-effect)
Duck (or more probably, DUKW)
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