steady exposure tool?

The cameraman shot with "automatic exposure" when he shouldn't. The exposure jumps when big light things enter or leave the frame. It's a fixed tripod shot; there are patches in the frame where there is no action and which should stay constant. How to make frame-by-frame brightness adjustment cued to one of those patches? Is there a facility in FCS3, or a plugin for FCP7, that does this?

In old (film) days we'd make a (net) gamma = 1 positive and blow up the little patch, much out of focus, to full frame, printing onto B&W negative developed to gamma = 1. Then bipack that negative with the positive. A corresponding DIY method is possible in FCP7, but I hope there's a jiffy tool now.

Dennis Couzin
Berlin, Germany

Progress report. The FurnaceCore plugin for FCP7 was said to do an excellent De-Flicker. But it might not work for the slower exposure changes in my case. Also The Foundry has discontinued it.

To DIY:
1. Transform the clip to "scene realm". That is, undo the BT.709 transfer characteristic, or whatever the camera used. I used this LUT.

2. Transform the clip to B&W.

3. Find a small patch untouched by action. Best if it is nearly detailless. Blur can be applied to help this. Mask the small patch and export.

4. Enlarge the small patch to full frame. Mine was so small it took two trips through FCP.

5. Average out the full frame. Since FCP lacks an "Average" filter I had to send an image sequence to Photoshop for this filtering. Now you have a varying ND filter.

6. Using Waveform Monitor determine the darkest it becomes: 28% in my case.

7. Transform all the values in the ND clip to 0.28/value (based on step 6). I don't think we have this kind of negative-making filter so I used this LUT. Now you have a varying ND filter to compensate the unwanted exposure changes.

8. Put the compensator over the original footage in scene realm. Modify > Composite Mode > Multiply. Render and export (or just rename the render file).

9. Transform the result of step 8 back into BT.709 realm. I used this LUT.

The result has steady exposure and looks beautiful.

Dennis Couzin
Berlin, Germany

Wow that is impressive. Thanks for the step by step.

Fantastic Dennis !

-Andreas

Some workflow tools for FCP [www.spherico.com]
TitleExchange -- juggle titles within FCS, FCPX and many other apps.
[www.spherico.com]

Thanks, VPiccin and Andreas. For those of us who can't program FCP plugins (which doesn't include Andreas), LUT writing is the next best thing.

Dennis Couzin
Berlin, Germany