The Toolset in Photoshop7

The normal Eraser tool simply removes the image back to the currently selected background colour. Again, like the Brush and Pencil tools, you can select all types of sizes and shapes of brushes to use as your Eraser tool.

Background Eraser actually erases the area to transparency. The result of this is that any layers below the current one will be visible in the transparent areas.

The Magic Eraser removes adjacent pixels of the same or similar colour to the one you click on. Like the Background Eraser tool, it removes the selection completely back to transparency

 
Sometimes a photograph doesn't process correctly in the lab. Expert photographers use certain tools to increase or decrease the amount of exposure - and this is where the terms Dodge and Burn come from.

The Dodge tool helps to adjust the lightness of the image. Stroke it over the area where you need to lighten the image - maybe a highlight that didn't get processed correctly - and Photoshop will lighten it gradually. By default, it lightens the midtones and leaves the highlights and shadows alone.

 

Burn tool is for when an image is over-exposed and darker areas are too light. Used in the same way as the Dodge tool, it also adjusts one of the three tones of the image - midtones, shadows and highlights.
The Sponge tool is used to increase the saturation of the colours in an image. In real life, a photographer might sponge a little extra processing fluid on a part of the image where the colours were a bit lifeless. The Sponge tool not only allows you to do the same thing, but it
gives you the option to desaturate the image too.
More tools