I searched the forum before asking.... I'm not even sure how to ask this properly... I have imported several layers from a photoshop file. Many of the layers are in groups to give me some pre-comp options in AE. On import, I did NOT choose to retain the layer size (or whatever that third option is) — I brought the file in just preserving the layers themselves. The precomps (when placed inside my master comp) have a bounding box that is limited to JUST that PSD's group content. However, if I open the pre-comp itself, all of the layers bounding boxes are scaled/sized to the size of the comp (in this case, 640x960). This means that the smaller layer items (say, a hand) has it's anchor point in the middle of the comp and the handles are on the perimeter of the comp. SO, even though the hand layer is only 200x200px in total size, I've got all the negative space included in my bounding box.
What I'm wondering is this: do I need to move everything out of groups in my PSD in order to be able to see the relatively appropriate bounding box? Or, is there a way to "crop" the bounding box so that it finds the widest and tallest distances of a layer's content (excluding the alpha) and then trim/crop/reduce/adjust/resize itself accordingly?
I'm not sure how else to ask it. Sorry.
Okay... so, I had the import types reversed in my head. Importing as "Composition", will force the bounding box of every layer to fit the width/height of the comp itself. Importing with "Composition: Retain Layer Sizes" will actually crop the bounding box down to the layer's content.
I thought retain layer size meant that it kept the size of the canvas, regardless of transparency in the layer.
Still, it would be nice to know if there is anyway to address that scenario in AE....
As you have already discovered, the native size of a layer's bounding box is defined at import by the means you choose to import. To reduce the boundaries of a layer after import, you use a mask. To increase the boundaries, apply the "Grow Bounds" effect.