Here’s a condensed checklist to complement the video:

1. Open the image
2. Select Layer -> New Adjustment Layer -> Levels
3. Give the layer a unique name or accept the proposed name
4. Select the Red channel
5. Position the black triangle directly under the histogram (not the triangle in the “output levels” section) to the start of the curve
6. Position the white triangle directly under the histogram to the end of the curve.
7. Repeat step 6 for the green and blue channel
8. Click OK
9. You’re done

Color Correction Using Photoshop Levels is a post from: Peter Bergdahl's Personal Blog