RGB Curves

Image -> Adjust -> RGB Curves...

This allows you to apply nonlinear correction on separate RGB channels.You can immediately see results on the image and Tone Curve.

With RGB Curves you can adjust the image color tone. This correction has similar characteristics to gamma for the values <1.0 enhancing contrast in the shadows for each channel.
For the values >1.0 the curves have (1-gamma) characteristics enhancing contrast in highlights (unlike gamma which decreases contrast in bright areas).

You can lock all sliders with the All together check box. Then all channels will have the same value. On some image values >1.0, RGB Curves may work better than Gamma adjustments, because the image contrast will be enhanced in its bright areas.

Moving all sliders to the right (All together) will enhance contrast in bright areas.

The original image had a blue cast. We can remove it by moving the red slider to 1.5 and Blue down to 0.8

We can create interesting color creations. R-0.4, G-1.2, B-0.2

RGB Midtones

Image -> Adjust -> RGB Midtones...

The RGB Curves are non-symmetrical (same as Gamma curve). RGB Midtones have symmetrical characteristics.

The RGB Midtones is just a variation of the RGB Curves with different type of curve affecting more the middle tones.

		Moving all sliders to the right (All together) will enhance contrast in bright areas.
		The original image had a blue cast. We can remove it by moving the red slider to 1.5 and Blue down to 0.8
		We can create interesting color creations. R-0.4, G-1.2, B-0.2