How to fix overbright backgrounds?

[acuriousman]

Hi all!

So recently I've been having a bit of an odd issue. I have an off white table with white stripes I use for recording. When I record something that is not filling a lot of the frame, I'm fine. But as soon as I film something that nearly fills the frame, the entire background gets blindingly bright and overexposed. This happens with two cameras I've tried. (Kodak Zi8, Sony Bloggie DUO HD)

Here's some pics to give you an idea.

This is ruining my shoots and driving me nuts! Any idea how I can fix this?

[edDV]

I don't understand the problem. The two frames have similar white levels from the table background and similar levels (within 3%) for the finger. Are you talking about the <3% difference? That would require locked manual exposure.





Black is 7.5% low but that may be due to the way you screen capped.

Explain the problem you are seeing.

[acuriousman]

I don't understand the problem. The two frames have similar white levels from the table background and similar levels (within 3%) for the finger. Are you talking about the <3% difference? That would require locked manual exposure.


[Attachment 12326 - Click to enlarge]


[Attachment 12327 - Click to enlarge]

Black is 7.5% low but that may be due to the way you screen capped.

Explain the problem you are seeing.

Sorry, wrong picture. Reuploaded.
See the massive difference? I want my video to look more like the first shot.

[jagabo]

Use manual exposure, not automatic exposure.

[acuriousman]

Use manual exposure, not automatic exposure.

Neither one of my cameras have manual exposure.
What else can I do?

[edDV]

Use manual exposure, not automatic exposure.

Neither one of my cameras have manual exposure.
What else can I do?

In the first case the differences are small. If you need to keep inside the 3% you need a camera with manual exposure that can be locked. Most cheap consumer cameras use a center weighted auto exposure that will get different results for a mostly dark center vs a light one.

This camera is doing a much better exposure than a typical cam (first posts).

The first case could be "fixed in post". The second is extreme. Difficult to impossible.

[poisondeathray]

If you had to "fix it in post" instead of re-shooting with manual exposure, one approach would be to use a luma key, duplicate the clip, composite behind a darker version . You would keyframe the levels /color correction parameter opposite to the changing autoexposure. This would only work if the "overbrights" weren't actually completely clipped (they look ok in the screenshot, at least on the right half, probably even more salvagable on the actual YCbCr video, because the some of the clipping probably occurred from converting to RGB for the screenshot).

It would depend how the shot was set up, you might have to do some rough garbage mattes, maybe combined with some motion tracking to automate some things, but the luma key would make it much faster than frame by frame rotoscoping.