GH2 What causes exposure fluctuations?

[Fly-catchers]

I was going through some recordings I did a while back on the GH2 using the 14-140mm lens. These were done on a tripod with the exposure on manual (160 iso, 1/50th, F5.6). Focus was manual and there were two similar recordings one done at WA the other medium tele. Auto white balance.

It was a sunny day no clouds and nothing was moving in the shot apart from the breeze gently blowing the leaves from the hedge at the rear of the shot. During the 3 minute recording the exposure largely remains constant but there are several occasions where the whole image darkens slightly and them a bit later lightens again. This happens a few times and yet the light levels was not changing- no shadows moving- sun going in and out etc. When these changes occur the whole picture is affected but the darker areas are where it is most noticable. Any ideas? I can only guess its the white balance as that was the only setting left on auto? Would that cause the image to darken/lighten?

 

[LosVideo]

I don't think it was the auto white balance as it wouldn't effect the iris. I have seen this happen as well, I notice while shooting that the exposure meter at the bottom center of the LCD fluctuates between + and - even though everything is on manual. I'm sure this is what it is, but I'm not sure how to take this option off. Anyone?

 

[Jim Simon]

You say exposure was on manual. Shutter too?

 

[dvbrother]

Is iDynamic turned on? If so, that could cause it. Is the shot locked down? Fixed focal length, or are you moving or zooming the lens?

 

[Fly-catchers]

Is iDynamic turned on? If so, that could cause it. Is the shot locked down? Fixed focal length, or are you moving or zooming the lens?

Yes iDynamic was off (never used that so far). No zooming of the lens during the shot just set up prior to shooting and left. Manual shutter. I know that Panasonic does some processing of the shots for its own lens and wondered if that had anything to do with it? Lousy weather at the moment but might try both with fully manual lens and also try the Exposure lock (even although I would not have thought it was needed for manual exposure shooting).

 

[Jim Simon]

How are you viewing the clips? I wonder if the player might be affecting the display of the media somehow.

 

[Fly-catchers]

I use Power DVD 11, Windows media player and VLC. All display this exposure change.

 

[Jim Simon]

Well, I can't think of anything else in the normal realm of things that might cause this. The only other possibilities that come to mind are a malfunctioning camera, or observer error (meaning you actually did have i.Dynamic on, or it really was auto-shutter and not manual).

I can only add that I haven't seen this kind of thing with my own footage.

 

[Prendi]

Hmm, no zooming... OK, I thought that was the issue. Are you sure you have everything on manual? I'm sure I had this the first day I had the camera and I had to change something, but for the life of me I can't remember what it was.