Adjustment Layers
Curves Adjustment Layer
I think Curves would have to be the number one most requested
enhancement for Elements. Though before you get too exited - I came
across this function in Elements by accident and after trying it a few times
decided that Adobe didn't really mean it to be included as it doesn't work
properly. I found that for small adjustments it seemed to work, for
larger settings there were wild unexpected color shifts and other strange
effects. I have included it in my tools as you might find a use for
it, but if it doesn't do what you expect then "Sorry, talk to Adobe - not
me".
Using the Curves Adjustment Layer is just like in Photoshop 6 but it only
works on the Master Channel and you can't edit the setting once you click
the Ok.
Curves is much too complex to explain here - any good Photoshop book will
have an in depth description of its use.
Channel Mixer Adjustment Layer
Unlike the Curves Adjustment Layer the Channel Mixer Adjustment
Layer does seem to work correctly, but it is still a bit limited as you can't
change the settings once you click Ok.
The Channel Mixer lets you modify a color channel using a mix of the current
color channels. This allows you to make color adjustments not easily
done otherwise. Also it is ideal for creating high quality grayscale
images by choosing the percentage contribution from each color channel.