I was thinking of getting one to film wide lock shot of theatrical performances . When I was playing around with one, every time I changed the aperture or iso the exposure would jump or step. Is there a menu setting to make seemless gradual changes? I assume auto exposure mode would do this but I'd rather be in full control of my settings.

The GH4 has a full manual control feature.

As far as I know there is no way to do smooth exposure changes on the gh4.

If that's the case I'll stick with a standard camcorder.
Thanks

If you use manual shutter speed and manual iris, coupled with Auto ISO with an upper limit to keep noise from appearing, and the camera is stationary with a fixed angle of view, how dramatic are the stepped changes in exposure from the camera as the lighting changes?

I don't have one to experiment with myself, but would it be dramatically more noticeable than auto iris on a traditional camcorder for a show with widely varying light levels?

The gh4 has no way to do auto iso in video mode but when you change the dial to "M", the auto iso option appears when you press the iso button on the camera. From what I have read it is changing shutterspeed to compensate for exposure changes and you can change that by tapping the "M" in the red box in the top left corner of the touch screen, and then switch to e.g. Aperture Priority mode which would allow auto iso with more gradual changes in exposure.
I have played a bit with the autoexposure on the GH4 when I just got it and found it to be unusable and unreliable, since there is no way to do gradual manual exposure changes on the GH4 I always changed the expsoure with the dials on the camera, it does show visible jumps in exposure when you change it but that's what happens if you try to use a photocamera as a videocamera.
For recordings where I need to have smooth expsourechanges, either in manual or automode I much prefer to use a dedicated videocamera, they are way better in handling this.