Author Topic: Timelapse ramping, AETTR, deflickering, etc.  (Read 542 times)

laidman

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Timelapse ramping, AETTR, deflickering, etc.
« on: February 28, 2018, 03:20:44 AM »
So I've spent some time going through the AETTR, timelapse deflicker, and advanced intervalometer threads and have (inevitably) come away with a few questions.

I had AETTR on, as well as the XMP files for deflickering in Bridge, and had a few keyframes set (using global time) around sunset.

I had the max AETTR shutter time set at 1/15 ( I think), although the max keyframe-set shutter time was 1 second. I was using a fully manual lens, so only adjusted the shutter speed and ISO.

It seems that AETTR overrides the keyframes to an extent, as I have adjacent images, one taken at 1 second, and the other at 1/15.

Looking at the images, it seems like AETTR does a pretty good job at metering the scene and maximizing the exposure, performing it's own sort of 'ramp' as it does its thing. As long as you're OK with varying shutter speeds and have a fairly consistent light fall-off, then could one only set this and not set any keyframes?

I loaded all the files into Bridge and used dmilligan's script to deflicker, which worked really well! However, as could be expected, the images shot at 1/15 were pushed really hard to match exposure, and so are really noisy. I'm going to try the Lightroom plugin for the next one I do. It works great. Thanks for this, dmilligan.

I'd really like to set AETTR, have the XMP files to deflicker in post, and just use the basic intervalometer settings, leaving the max AETTR shutter time at something pretty long, like 10 or 15 seconds. But it seems like you can only ramp ISO (and aperture) with the advanced intervalometer. I suppose that if you're going from bright daylight to dark, clear night, you'd really want to dial in an ISO ramp then, too...Any way this could be incorporated into the AETTR settings? Or am I missing something here...

Regardless, I was really impressed with my first-time results.

 

a1ex

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Re: Timelapse ramping, AETTR, deflickering, etc.
« Reply #1 on: February 28, 2018, 12:21:51 PM »
It seems that AETTR overrides the keyframes to an extent, as I have adjacent images, one taken at 1 second, and the other at 1/15.

Yes, the two tools are independent (so they will conflict - both tools will attempt to change the shutter speed if you ask them to do so), but I agree some integration would be nice (maybe adding another parameter that would ramp ETTR's shutter limit).

A while ago I tried to perform a similar ramping using an undocumented feature in AETTR: it limits its exposure to interval time minus 2 seconds (if its own limit is larger than that). In my case, I wanted pictures every 30 seconds of a daylight subject near 7 and 9 pm, but I wanted 5-minute exposures during the night (as I didn't want to use additional light sources); the interval wasn't critical during the day (could have been a minute or two). So, I ramped the interval, and AETTR adjusted itself. This part worked well.

All the other timelapses I've tried were with plain AETTR (simple configurations, without any sort of custom ramping, other than letting ETTR to do its job).

You should be able, however, to ramp the aperture manually with adv_int without conflicting with AETTR.

laidman

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Re: Timelapse ramping, AETTR, deflickering, etc.
« Reply #2 on: March 03, 2018, 07:29:19 AM »
Thanks, Alex

So I tried a second one. I ramped the ISO from 100 to 1600 over the course of a 12-minute period, which was way too quick, it seems. I was using a fully manual lens again, so this was the easiest option.

I've linked the resulting video, and during the middle the sky does some weird grey shenanigans. I think this is from it being blown out, and then having the highlights pulled down in Lightroom. I gave up too much to the highlights, too, I think. Not much sky detail at all.

Next time I think I'll just let AETTR do its thing, for as long as varying shutter speeds don't affect your output, you can really get a lot out of going from say, 1/60 to 10 seconds.

dmilligan's deflicker script worked well again. I ran 8 iterations in Bridge CC. On my previous attempt I gave it 15 and it still said more could be required. This time it took the 8 and was fine with them. I wasn't able to get the deflick.lrplugin working in Lightroom, so my workflow thus far has been Bridge -> Lightroom -> After Effects.

Anyway, it seems like perhaps AETTR could benefit from having some more specific parameters built in, like an aperture and ISO option. Essentially taking the ramping functionality from the adv.int. You'd set your desired highlight, midtone, and shadow levels, and then let AETTR do its thing while having access to more than just a shutter ramp. Add in an 'always maintain exposure or else increase/decrease' (depending on sunrise/sunset) option, and you're gold! The deflicker plugin seems to work really well.

A very powerful tool, this! I think it'll take a little (lot) more fine tuning on my part to set the ramp timing correctly.

https://www.youtube.com/watch?v=cWL0bg7REwg

a1ex

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Re: Timelapse ramping, AETTR, deflickering, etc.
« Reply #3 on: March 03, 2018, 09:34:14 AM »
Yes, that's from overexposure. For timelapse, it's probably best to lower the target level a bit, to leave some headroom for exposure variations. Overexposure is also the cause for very dark images right after that (as it doesn't know how much to go back).

BTW, by default, the deflickering script meters on the median - which, in your example, falls right between the sky and the ground (so you've hit the edge case where median is not the best choice). Try a composition with either more sky than ground, or viceversa.

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... having some more specific parameters built in, like an aperture and ISO option.

Aperture is useful (though I should define some criteria - when should AETTR change it?), but what should it do about ISO? (I want to update it with the findings from ISO research, to make a better choice, but don't see what options should be in the menu).

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Add in an 'always maintain exposure or else increase/decrease' (depending on sunrise/sunset) option, and you're gold!

Tried that, and found out it's a trap. In my tests, the exposure wasn't always fully increasing or fully decreasing - there were short periods where exposure direction changed during a sunset. Limiting the direction could result in short periods of overexposure or underexposure, that won't be corrected because of this restriction.

However, limiting the exposure increments (for example, don't correct by more than 0.5 EV from one image to another) could help.

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as long as varying shutter speeds don't affect your output

This can be an issue - I'm thinking to exploit the full-res silent picture capability, and take images with a "fixed" exposure time - usually interval / 2, to get a 180-degree shutter in the resulting video. If the scene requires a lower shutter speed, the silent picture module would take more images and average them into a single picture.

This trick can be used for reducing temporal aliasing, too (just never got around to implementing it), but the low-level stuff required for this is documented.