Deflickering time lapse

When ever we shoot time lapses we always go to manual mode, yet it is not always possible. Especially with the holy grail of time lapse – sunset / sunrise. Delfickering time lapse is the hard part. Such time lapses are the most tempting ones, and also technically cumbersome, almost, because there is a twist.

You have to shoot them them in one of the 4 ways, manual exposure (you control the shutter speed), Av priority automatic exposure (camera controls the shutter), bulb ramping (intervalometer changes the exposure by a set curve or keyframes) or the last, and my favorite, auto ETTR if ML. Problem is tough, as I mentioned earlier is that all of them require deflickering, either manually for the first option or other ways for the rest of them.

One of the solutions comes from Magic Lantern (ML) – deflicker module, which in conjunction with auto ETTR.  It creates sidecar file that contains exposure correction calculated so that it would remove the flicker, in software that supports it.

defilcker module

Settings are rather straight forward and go as fallows:

Slidecar file type: Only two options are available: UFRaw and Adobe XMP, as I use mostly Adobe i have it Adobe XMP, so it works in Bridge, Adobe Camera RAW (ACR), AfterEffects

Deflicker percentile: 50%  This determines where to meter the exposure for the deflickering process.  50% is recommended and is equivalent to metering in the Median highligts.

Deflicker target level: -4 EV.  As much as I understand this is the value it try to keep the 50% exposed areas as. I have to do more research into this, honesty I just leave it alone.

Unfortunately this is not the end of the story – the algorithm sometimes does not perform as required, or adobe rejects the xmp file, once in a while, so you have to browse trough and fix the ones off by hand in ACR. Other problem is that resulting time lapse would need further adjustment in exposure, or even ramping, and that should be done first at the RAW realm in nondestructive  manner in the xmp files. There are many grate tools, but I have found one I like – it is called Bridge Ramp by David Milligan. It also has a deflicker algorithm, but it is slow and why you need to do it later if camera has already done that? This tools is grate – you can set first frame and the last frame as you want and it will ramp the value or values you selected either absolutely or relatively (you tick the additive check box). The last option is awesome – it will keep the deflicker data you have, but will relatively change it to your liking.

Ramp acr

You can use this script even on JPEG, if you cheat a little – make the ACR to generate xmp files, by just simple task in it, like lens correction. Then run script to you liking, but you have to export the result – AfterEffects ignores the xmp files for non raw images, and sometimes even raw as i found out when working with Dual ISO DNG raw files.

When ever you set time lapse remember to leave interval for the ETTR and defklicker modules to run, 1-3 seconds, otherwise you will have either wrong exposure or missing XMP file.

For further reading:
Flicker Free ETTR Time lapse
Script for deflickering and ramping ACR (.xmp) settings in Bridge
ETTR + DUAL ISO = 14 Stop Dynamic Range Timelapse

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