Maintaining scale when moving an object in Z space

I'm surprised that this isn't a popular question.  It's something I've done often and easily in Apple Motion and I can't believe it is not easy with AE.

Is there a way to maintain the scale of an object when you move it in Z space?  In other words, suppose you import a PSD and want to place the layers at different depths in Z space, but still want to maintain the proportions of each layer.

I'd appreciate any advice.

Thanks!