It's important that you compare the original version of your photograph to the edited version.
Otherwise, you can't accurately judge the quality of your editing.
In the Adjustments panel, there are several icons at the bottom.
Look for the icon of an eye with an arrow.
It's the third one.
1) Click and hold the eye/ arrow icon.
The Levels adjustments disappears.
2) Release the mouse button.
The editing you did with Levels reappears.
Go back-and-forth between the with-Levels version and the no-Levels original.
Do you like the result?
If not, readjust the sliders.
If you're in the Adjustments panel—and want to go back to the Layers panel—click Layers.
If you're in the Layers panel—and you want to readjust the Levels sliders—double click the icon in the Levels layers.
Keep the Levels adjustment layer on top of the stack of layers.
In that position, it will "broadcast" the corrections to all of the layers below.
As you continue editing, you may create new layers.
As you do so, make sure the Levels adjustment layer stays on top.
If another layer is created above it, do the following.
1) Click and hold on the colored part of the Levels adjustment layer.
2) Drag it to the top of the layers stack.
Often, it won't go there.
You'll see exactly what Levels does with the step wedge below.
Do the following.
1) Download the step wedge.
2) Open it in Photoshop Elements.
3) Create a Levels adjustment layer.
4) Experiment with the sliders.
Changing the Levels may change the overall color of the photograph.
If the color changes, and it's not acceptable, change the blending mode of the Levels adjustment layer from Normal to Luminosity.
At the top of the layers stack, look for the unlabeled Blending Mode box.
It's to the left of the Opacity box.
If you're new to blending modes, go to Blending Modes.
By switching from the Normal blending mode to Luminosity, you're disconnecting luminosity from the color.
You're "turning off" the color of the Levels adjustment layer.
There are other methods for adjusting Levels.
Go to Other Levels Methods.
Levels is just one of several adjustment layers.
Go to Adjustment Layers.