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Any leads for fixing variably stretched images from a scanner?

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joel penner
Any leads for fixing variably stretched images from a scanner?
on Feb 23, 2020 at 3:30:38 am

So I have an obscure problem. I take timelapses using computer scanners. Right now I am watching a fungus colonize legumes (tempeh). The motor and/or belt on one of my scanners is acting up. In some photos it will go a bit slower on some portions of the scanner platen, which has the effect of making those portions mildly stretched. When these images are rendered into a video it kind of creates a shimmering effect.

I had this problem before, but it turned out that the problematic images were stretched uniformly, so I was able to create a Photoshop action where I stretched them back using Free Transform and it fixed the problem. The problem with this timelapse is that the stretching happens very subtly and non-uniformly so you would have to go image by image and determine which portions of each image are stretched, and manipulate them back to how they should be. That would be very hard to do manually.

Maybe this would be in the domain of a different program, but would there be any way within AE to detect which parts of the images in the sequence are stretched and stretch them back automatically? I realize that this is a complicated and obscure problem that might be hard to fix in post.

Here's a video showing the problem:

https://www.dropbox.com/s/6qm5szcgpi92t90/tempeh-shimmering-small.mp4?dl=0

Here's an image sequence if you'd like to experiment:

https://www.dropbox.com/s/my7nere6vpl1fqn/letter-tempeh-stretched-images.zi...

Any leads would be much appreciated, thanks!


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Graham Quince
Re: Any leads for fixing variably stretched images from a scanner?
on Feb 23, 2020 at 9:38:40 am

Oh wow, I can imagine this being frustrating.

Pure speculation here, but how about including tracking markers, then using AE’s tracker to track the scale changes. You might then be able to reset the scale based on this information.

You might need to break up the image into bands and track each section separately.

I’m also wondering if there’s anything within the time displacement effect that could help here.

http://www.YouTube.com/ShiveringCactus - Free FX for amateur films
http://shiveringcactus.wordpress.com/ - FX blog


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