Isolating growing microbial colonies from condensation on petri dish lid

[featheredtar]

I did multiple timelapses of microbes growing in petri dishes. There was a bit of condensation on some petri dish lids. What would be the best way to remove it? I am then planning on compositing the different microbial colonies into new arrangements.

I tried doing doing a reverse key of the microbes to isolate them using a track matte, but some of the colour of the condensation is similar to that of the microbes so it didn't really work. I have also thought I could create masks for the different microbes which automatically grow as they grow to isolate them from the background of condensation.

What do you think the best approach would be? The ideal solution would work for microbes of different shapes and colours, and would involve as little manual rotoscoping as possible, but if you can think of a relatively-simple solution that works for most but not all of the microbes that's great too. The video file is below if you want to experiment. Thanks.

Dropbox - petri-condensation.m4v

[Mylenium]

Unless you plan to work your fingers off for the next half year, there is no way to even semi-automatically separate the droplets and rainbow refractions from the actual bacteria. There simply is no distinct color that could be latched on to extract a matte without one part interfering with the other.

Mylenium

[featheredtar]

That's what I thought, thanks!

[Dave_LaRonde]

Yeah, you're pretty much hosed.  No way to isolate the bacteria only.  You'll have to console yourself with the thought, "I got a pretty neat time lapse" and leave it at that.

[Rick Gerard · Accepted solution]

There is not much you can do with this image to get rid of all of the condensation:

You might go to the last frame of the video, export a still, paint out or clone everything you don't want in the final shot, duplicate that layer, jack up the levels on the original until you have nothing but the final state of the microbes as white spots on black, then use that as a track matte for the fixed layer. Once you have poked holes in the layer were the microbes end up you can use that as a track matte for the footage. It will eliminate most of the drops of condensation.

[featheredtar]

I'll try that, thanks!