Editing a copied precomp without changing both/original one.

[WernerHeisenberg]

I have a 190 layers in a composition which I pre-comped. Now I create a copy of the pre-comp so that I can edit the copy without editing/changing the original one. 
But any change I make in the copied pre-comp layer, changes the original one. Even locking the original one didn't avoid edition. 
I even tried importing separately, nothing worked so far. 
How do I do so? 

[Mylenium]

Without any info about your actual project we can't really tell you much, but it seems you are unaware that you need to actually duplicate and replace every and each pre-composition in the project as well. If you really have that much stuff, you may want to look at scripts like True Comp Duplicater over at AEScripts.com. Anything outside that will require to show us screenshots of your project panel, the flow graph and info on where on how those layers are used.

Mylenium

[WernerHeisenberg]

Hello, please see the screenshot below: 

I have an illustrator file of a map. I am trying to 'matte' a video under layer of a district. The district layer '317' opacity changes from 100 to 0% and the video appears. 
But when I alpha mat the layer in video, the video opacity also disappears. 
That's why I wanted to have a copy of layer 317 and other districts on which I intend the same animation, to have 100 opacity to apply that on video layer as matte. 

[Szalam]

I just did a project where I had a camera flying out of shot footage matted into a country on a 3d globe, then we followed an object around the globe to the next country into which we flew which then faded into another matted piece of footage.

I used Essential Properties to do this as Roland suggests. The globe image was a preecomp and, inside the precomp, the movement of object we were following was promoted to essential properties and the opacity of the necessary countries was promoted as well. 

Then, I could duplicate my globe spinning comp as many times as I needed and animate the globe spinning and then animate the essential properties on the map layer. WAY easier when client changes came in to just fix one map precomp vs. a dozen.

Easy peasy!

[Rick Gerard]

Duplicate your pre-comp in the Project Panel. Duplicating in the timeline does not make a unique copy of anything. It's just a copy of that layer.

You should spend some time with the User Guide. This is one of the basics that are covered there.

[nojo339195239059]

doesnt work for me, when i drag into the timeline after that it still does the same thing

[Szalam]

If you duplicate your comp in the project panel and then change something inside of the new version, it will be unique from the earlier version.

That said, if there are comps inside of the comp you're duplicating, you'll have to duplicate them too (and re-nest them in the duplicated main comp). Or use the True Comp Duplicator script. Or use Essential Properties (but those may have to be expression-linked through levels of precomp nesting).

[Roland Kahlenberg]

Use AE's Essential Property feature which allows you to make changes to this Essential Property without affecting the original. 

More info here - https://helpx.adobe.com/si/after-effects/using/essential-properties.html