Yes, Photoshop Elements has a selection Brush. And, No, Photoshop CS3 doesn't. Photoshop has other selection tools.
Quick Mask is probably the closest to the PSE Selection Brush. When you activate Quick Mask, you paint on the image to create or modify a selection like you do with the PSE Selection Brush. It works a little differently though and actually has more capability than the PSE Selection Brush.
You enter Quick Mask mode by either clicking on the Quick Mask Mode button in the tool bar or typing the letter Q. You exit Quick Mask mode by clicking on the button or typing Q again. Before you use Quick Mask mode, I'd recommend that you change the default setting for it. Double click on the Quick Mask mode button in the toolbar and choose the Color indicates "selected areas" option. The default is the "masked areas" option and that leads to a lot of confusion for most people. "Selected area" is a lot more intuitive. It will also look like the PSE Selection Brush in that tool's mask mode.
quickmask.jpg
When you enter Quick Mask mode, you will paint on the image with the Brush tool to modify the selection. The foreground and background colors will automatically become white and black and you can switch between them by using the X key. Black will add to or create a selection, and white will remove from a selection. You won't see marching ants, instead you will see a red overlay. If you changed the default to "selected areas", the red area represents the selected areas. When you exit Quick Mask mode, the red areas become a selection and you will see the marching ants.
While in Quick Mask mode, you can use the other selection tools to select a portion of the image to fill with black or white or gray and you can use filters like gaussian blur (or the blur tool) to feather the selection. A soft brush will have a feathered edge, a hard brush will have a hard edge.
In addition to the Quick Mask mode, take a look at the Photoshop Quick Selection Tool also.
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