Author Topic: Post deflicker - images getting too dark  (Read 1998 times)

nchant

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Post deflicker - images getting too dark
« on: March 29, 2016, 04:03:54 AM »
Hey guys,

I recently shot a timelapse (holy grail) of a sunset to night time, however the settings weren't changing until the overall luminance/brightness (?) of the exposure got down to 10%? Is this normal? Can I or should I change this to 20% and if so, what setting changes that?

Probably a noob question but not sure what to do :)

The timelapse ended up being really nice, can be seen here – Easter Auckland: https://www.facebook.com/mackphotographynz/videos

Thanks!

a1ex

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Re: Post deflicker - images getting too dark
« Reply #1 on: March 29, 2016, 02:24:20 PM »
Post Deflicker simply writes some exposure metadata to postprocess the image. When you say "the settings weren't changing until the overall luminance/brightness (?) of the exposure got down to 10%", you are probably referring to the auto exposure method you have used (Canon meter, AutoETTR module or AutoExpo module).

For the existing footage, you have those options:
- You could write the script that changes all exposure values from the sidecar files by a constant amount (the hard way)
- You can run a different tool that re-computes the exposure compensation data from scratch (easier):
  - if you use Adobe software, try this script
  - for an open-source workflow, try the Deflicker module from darktable, which was actually ported from ML.

For ETTR, you probably want to increase the SNR limits, or allow more clipped highlights. Without seeing the actual images, that's my best guess.

nchant

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Re: Post deflicker - images getting too dark
« Reply #2 on: March 31, 2016, 02:04:44 AM »
Thanks a1ex!

What I mean is I started the shoot at these settings:

1/125s
ƒ9
100 ISO
48% brightness (?) was the marker on the screen.

And after 30 mins of shooting, the brightness was down to 10-11% but the exposure settings were the same?

Audionut

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Re: Post deflicker - images getting too dark
« Reply #3 on: March 31, 2016, 02:09:09 AM »
Was the scene luminance changing?

Post deflicker only processes already captured files.  It's mainly for fixing small exposure changes from differing exposure settings.

If you want the actual exposure settings to change while capturing a sunset or whatever, you also need to use something else like AutoETTR.