PHOTOSHOP TIPS FOR AVIATION PHOTOGRAPHERS - ADJUSTING COLOUR USING A CURVES ADJUSTMENT LAYER
(1) Create a separate Curves adjustment layer.
(2) On the RGB channel select the right-hand eyedropper. Move the eyedropper onto the brightest point on your image and click. You have now defined the White Point (highlights).
(3) Now select the left-hand eyedropper. Move the eyedropper onto the darkest point on your image and click. You have now defined the Black Point (shadows).
This technique is very quick especially when you can easily identify the highlight and shadow areas of your image. However, sometimes these regions are not so easy to identify. In this case a Levels adjustment layer can be used to adjust colour.