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When I shot the video, I forgot to fix the exposure, so now the brightness constantly changes. How can i stabilize exposure in video, I can't reshoot it.
Plugin Flicker Free didn't help. The video goes for an hour, not possible to fix it manually.
Example of video
I have planned for a long time to make a video luma stabilizing software, and when I saw this question I gave myself a kick in the butt and built something (hopefully) useful during the night. Now, it's by far a finished and polished product, of course, but if you feel bold and want to give it a shot, here is how you can use it (currently).
The best part: it's free... (and runs locally directly in the browser).
Prerequisites:
Go to this web page to start:
https://epistemex.github.io/Video-Luma/
As mentioned, everything will run inside the browser (there is no upload) and will require a newer HTML5 browser. I am using Firefox v59 beta for this myself, but you should be able to use v58 stable as well as Chrome, Opera, Edge, Safari etc (although the latter ones may be slower and I have not yet fully tested with these browsers except Chrome).
Then hit the "Analyze" button and wait until end. How fast it will finish depends largely on your computer specs. There is no escape in this version, but you can always reload the page or close the browser if you feel it will be too slow (in that case consider using lower size frames).
When done you can hit the "PREVIEW" button to get a impression of how it will look. It's not gonna be perfect. Currently I'm just using luma to adjust the values (I plan to support white-balance as well) but you will, depending on the footage, see variations in contrast. Not perfect but hopefully better.
Finally in the web page, hit 1) "Export" and 2) select+copy all the text AS-IS:
The key-frames should now show in the right pane and you're ready to go! Preview and check if everything looks fine.
I noticed a bug in the browser's image loading process which can produce "spikes" in the data from time to time (unclear why but I'm working on it):
The only current way to get rid these is to open the 1) graph panel in After Effects and 2) manually remove those:
I did implement a "Spike filter" button that is activated if these are detected, but there is a chance it will affect the other data as well so I would recommend not using it for the time being.
I have not run exhausted memory tests but the images are loaded one by one directly from disk as to not to fill up the memory too much so you should be able to run through long sequences although they may take some time.
And that's it, let me know if it's useful in your case (or if something went horrible wrong - which reminds me to add a disclaimer: use at your own risk! :) ).
Q: When I shot the video, forgot to fix the exposure, so now constantly changes the brightness ... The video goes for an hour, not possible to fix it manually".
Use "Tonal Exposure" in Lightroom.
The thinking and theory behind dynamic and tonal range:
TutsPlus - "Light & Photography: Exposure and Tonal Range Consideration":
" Ansel Adams devised what is known as the Zone System. The zone system can be applied for obtaining correct exposures under different circumstances no matter how tricky".
Use Lightroom's tonal exposure to match all images to a mid-range image by choosing that image first and individually; then select the rest. You need to treat the video as a series of images if you feel there's to much to adjust, you may want to break it into scenes since you wouldn't want bright outdoor scenes to be too dark and very dark scenes to be overly brightened. Even if you broke 60 minutes into 60 scenes it's not going to take an hour to fix.
Adobe Help - "Color and tonal correction basics".
YouTube Tutorial: Terry White: "How to Match the Exposure Across Photos In Lightroom 5".
