Hi [USER=133437]@GracieAllen[/USER]
First the bad news
The problem that you see is not limited to use of Smart Objects.
Any time you change pixels above another pixel Layer or masked adjustments Layers, and then go back and change the underlying pixels (whether in a Smart Object or not), those underlying pixel changes are done independently of the Layers above. So this can cause a lot or rework or throwing out Layers. One must be careful in creating the Layer Stack to avoid those situations whether it is a Smart Object or any other pixel Layers below.
There is a way to help with this problem so you can access the Camera Raw Filter or any other filter and have it apply to multiple Layers (so now the good news)
All you have to do is select all the Layers you want adjusted together and turn that into a Smart Object (even if one of the existing Layers is already a Smart Object).
Then, when you apply Filters to this new multi-Layer Smart Object, they all get adjusted together.
When you include a Smart Object by itself with or without other Layers, this is know as a hierarchical Smart Object. It can come in handy in many situations and your is one.
As a specific example
1) Make one Layer a Smart Object and make Filter adjustments (know when in a Smart Object as Smart Filters).
2) Make a second Layer with pixels that interacts with the Smart Object below
3) Select both of the these Layers and turn them into a Smart Object - now you can adjust both at the same time and the results won't be trashed.
Also note that this is non destructive. You can go back into this multi-Layer Smart Object and make additional changes.
So whether it is Photoshop or any other graphics editor that supports Layers, you have the same issue of careful construction of the Layer Stack to avoid the problem you see. Hierarchical Smart Objects can help to some degree get around those problems.
Hope this helps
John Wheeler
