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How to deal with fluctuating zoom - Printable Version

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How to deal with fluctuating zoom - macoda - 2019-02-08

Hello All,

I'm working on a time-lapse of the recent lunar eclipse that I shot and being the newbie that I am was not careful enough to gaffer-tape my 16-35mm lens so as to lock the zoom at 16mm for the whole sequence. Because I'm in Ireland and it's constantly humid here I had to wipe the lens every 5-10 minutes throughout the whole 7 hour shoot, in temps where the windchill was -6 degrees Celsius. I was gripping the zoom ring through thick gloves to prevent it from moving, or so I thought, but with a preview now rendered can clearly see there was some slip throughout the shoot. I could deal with it if it was consistent over the sequence, for e.g. going from 16mm at the start to 19mm at the end, but it's hopping around from 16mm to 18mm, back to 16mm, up to 20mm, back to 16mm.....you get the idea.

I've tried Warp Stabilization in After Effects, and that got me close to resolving it, but there's a point in the sequence when the Moon is fully eclipsed, but shrouded in cloud, so the scene is essentially dark, with very little showing up on the histogram, and pushing exposure etc just leads to a muddy mess, and that's where After Effects struggles to apply stabilisation, so it goes haywire at this point in the sequence trying to find something to stabilise off, and the resulting output is just not useable.

So, correct me if I'm wrong, but am I looking at having to edit each of the 1800 or so images individually, where I take the 'worst' image, i.e. the one that's at 20mm, and crop the rest off anchor points in that, or is there a less laborious/more efficient and effective way of stabilising the zoom across the sequence so that there is little or no judder?

I have all fingers and toes crossed that there's a solution to this other than having to individually crop each one.

Thanks,

John


RE: How to deal with fluctuating zoom - gwegner - 2019-02-09

You can keyframe the crop in LRT as explained here: https://forum.lrtimelapse.com/Thread-ken-burns-effect
Maybe that can help you to find a way to aproach this problem.


RE: How to deal with fluctuating zoom - macoda - 2019-02-15

Thanks for taking the time to reply Gunther, and for your suggestion. I figured that if I wanted the best result, with minimum loss, that cropping each image was the only way to do it, so I've 1,400 of the 1,800 images done now. The result is in line with my expectations, with some minor juddering visible, as it's nearly impossible to get exacting crops (in Lightroom) in some instances. What I may do when I'm finished is to use a very subtle Ken Burns effect as you suggested to see if that will smooth out the remaining judder.