Do you mean Photoshop CS4, the current version?
Or do you actually mean Photoshop 4, from thirteen years ago?
From: 3Ring Binder
ok, so i make a layer in PS and fill it with color or pattern.
then i edit the layer with the eraser tool, or whatever.
now, i want to fill that layer with a new color or layer, but it fills in the entire layer, not just the parts remaining?
how do i "re-fill" (with a new color or pattern) only the parts of the layer that have image and not have it 'refill' the entire frame?
So you know, there are many different ways to fill an area with a color and/or pattern. From what you're saying, it sounds like the method you've been using is the Edit -> Fill command (Shift-F5). Here's a quick tip for you. Any command you execute from the main menu bar (fills, strokes, image adjustments, transformations, filters, etc.) will always affect the entire canvas, unless you form a selection first. Think of the main menu as your brute force tools, and the toolbox as your finesse tools.
The short answer to your question is form a selection. After you do your erasing, simply ctrl-click on the layer's thumbnail in the Layers panel (or Layers palette, if you're using an older version of PS), to select everything on the canvas. Transparent areas will remain unselected. Then apply your new fill, and the unselected areas will remain unaffected.
The better answer is you really should be using more powerful tools than just blanket fills, and you most certainly shouldn't be working all on one layer. We could talk all day about that, though, which would be pretty well beyond the scope of a forum like this. So I'll just leave it at that.
The last thing tip I'll add for now is that it's not the best idea to use the eraser for the kind of work you described. That's really not what it's for. It's meant to be used in conjunction with the paintbrush or pencil, for cleaning up as you go while painting or drawing. If you draw a line that didn't quite come out right, erase it, and draw a new one, just like you would with the eraser on a RL pencil. That's really it.
For the kind of operations you were describing, layer masks are far more powerful, infinitely more flexible, and actually much faster than the eraser could ever dream of being. I'd strongly encourage you to forget that that silly eraser even exists.
Just so you're aware, had you masked the areas you wanted to hide instead of erasing them, it wouldn't have mattered in the slightest that your new fill was covering the whole canvas. The original mask would still apply, and the hidden areas would still be hidden. See what I mean about faster? Plus, you'd have the added benefit of being able to unhide those areas any time you want, simply by turning the mask off, which is something you could never ever do with the eraser.
Always favor non-destructive tools over destructive ones, wherever and whenever you can, and you'll always have an easier time.
