Yes. I have done the test on olympus in start and stop preview, but maybe it is not the most logical "place". And maybe the test on olympus only is too "restrictive".
Actually, since the camera do not have mirror to be locked it do not have the corresponding widget in gphoto . hence gphoto do not find it. but the current (without this mod) gphoto_driver in indi check for this viewfinder widget (and need it) to work properly. It may be also the case for other 4/3rd mirrorless DSLR (pentax/lumix) dunno.

Joël

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