Curves (Photoshop)
With Curves you steer your image's brightness and color in Photoshop via a bendable line that maps the tones from black to white. Pull the line up for lighter, down for darker, and give it an S-shape for more contrast. Per RGB channel you can also steer the color specifically.
Add Curves as an adjustment layer, so everything stays editable and you get a layer mask right away. Click the line to set an anchor point and drag for light, dark or contrast, or pick a channel to push blue into the shadows, for example. The automatic mask lets you limit the effect locally, handy for dodge & burn or color nuances. Tip: use the on-image hand to grab exactly the tonal range you want to adjust.
Read also the in-depth explanation: Curves (Photoshop) explained.
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The presets on this site set these adjustments up for you as a starting point, which you then fine-tune to taste.