Can I develop film in oak leaf extract?

If you look at the results I would say you can. The developer was made up using the universal caffenol recipe and stand developed for 1 hour at room temperature. The only difference to the caffenol is there was no coffee - instead I collected fallen oak leaves - about 250 g worth (dry weight) and boiled them in water for 15 minutes, strained the dark brown solution away and used it as the solvent in the developer.

And it works.

So you can, if you have wash sod and vitamin C, make a developer out of the fallen leaves on your lawn. I should add I used oak leaves - which have a lot of tannin - other sorts of leaves may need more leaves to make a good developer.