From the Photoshop Help file:

"The paint bucket tool fills adjacent pixels that are similar in color value to the pixels you click.

....

To use the paint bucket tool:

1. Specify a foreground color. (See Choosing foreground and background colors.)
2. Select the paint bucket tool .
3. (Photoshop) Specify whether to fill the selection with the foreground color or with a pattern. (See Filling and stroking selections and layers.)
4. Specify a blending mode and opacity for the paint. (See Setting options for painting and editing tools.)
5. Enter the tolerance for the fill.

The tolerance defines how similar in color a pixel must be to be filled. Values can range from 0 to 255. A low tolerance fills pixels within a range of color values very similar to the pixel you click. A high tolerance fills pixels within a broader range.
6. To smooth the edges of the filled selection, select Anti-aliased. (See Softening the edges of a selection.)
7. To fill only pixels contiguous to the one you click, select Contiguous; leave unselected to fill all similar pixels in the image.
8. To fill pixels based on the merged color data from all visible layers, select All Layers. (See Sampling from layers.)
9. Click the part of the image you want to fill. All specified pixels within the specified tolerance are filled with the foreground color or pattern.

If you're working on a layer and don't want to fill transparent areas, make sure that the layer's transparency is locked in the Layers palette. (See Locking layers.)"

As I said, whether Contiguous is checked or not, PB does not affect anything outside the selection edges. But the area it fills is not dependent on the Magic Wand or any other current selection. Try it.

If you have a high tolerance set on your Magic Wand and a low tolerance set on your Paint Bucket the Paint Bucket will not fill to the edges of the selection, which I think is what Charles is trying to do. It will only fill the pixels of similar color as usual. The Paint Bucket is in essence making its own selection.

charles_s_corker

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Help neede with Paint bucket