This is a quick and simple technique for correcting the colour of an image in photoshop. It is not always successful and will not give you the desired results 100% of the time. But as it is quick and easy it is definitely one to try first.
My picture of Goðafoss has a dictinct blue cast. It was taken in low light and this is a common problem as my canon couldn’t really see well enough to decide on an appropriate white balance. I could have corrected this at the RAW stage, but for the benefit of this tutorial, I burned it as it came out of the camera.
Duplicate the layer. Then apply an ‘average blur’ to the top layer.
You will see the top layer converted into a big blue smudge (or whatever colour cast you are dealing with).
The next step is to create a ‘curves adjustment layer’ by clicking on the adjustment layer button on the layers pallet. Alternatively you can create a ‘curves adjustment layer’ from the layer menu. See more information on adjustment layers.
The curves dialogue box will open and you simply select the middle eye-dropper tool and click anywhere on the top layer.
You should see your top layer turn grey. The final step is to get rid of the top layer so that the curves adjustment layer is directly affecting the original picture.
You can now see the effect of the curves adjustment on your original image.
*Note: this can also be achieved with the middle eye-dropper on the ‘Levels adjustment layer’.