I have a wedding coming up in a month, and my normal assistant will not be able to make it. So I have hired someone who is decent at composition and all, but really has no idea how to use my camera and doesn't feel confident that they will learn it in time.
Will I be safe to leave the camera in auto mode? or should I just lock the levels before the ceremony and hope the lighting doesn't change that much?
I am afraid the camera will JACK the gain right up in auto mode.
What would you do?

Thanks

Depends on the time of day and how long the ceremony will last.

During the middle of the day, I'd probably set it in manual and lock it.

Early morning or evening and I'd put it in Auto and compensate it with a preference if you can.

Thanks

What do you mean by compensate it with a preference?

AE Shift. Page 50 on the manual. It allows you to control, to some extent, the automatic operation of the camera.

Will I be safe to leave the camera in auto mode? or should I just lock the levels before the ceremony and hope the lighting doesn't change that much?
I am afraid the camera will JACK the gain right up in auto mode.
This is a difficult call. You might test the environment during the rehearsal.

It depends on how even the lighting is where your assistant will be shooting, and on the coverage you expect him/her to get.

If the lighting is fairly even, and the framing will be fairly consistent (i.e., all wide/med or all CU shots), then you're probably safe with setting the exposure at the beginning for the assistant to use.

If not you might be better off with auto, but the assistant will have to watch for the hot spots -- like a bright light behind the subject.

Two things you do can about the gain:
1. You can set the gain and shutter in manual, and leave the iris in auto.
2. If you put all exposure in auto, then you can set the max gain the camera will use in the menus.

Good luck on your shoot and let us know how it goes.

What do you mean by put it in manual and lock it?

Doesn't lock just prevent you from accidently changing the settings?