To remove colour cast when using ND filters.
Method 1
Open the image to be adjusted.
In the layers palette drag the image thumbnail to create a new layer button (blank sheet of paper on bottom rhs of layers palette).
Go to filter > blur > average.
Go to image > adjust (or filter > adjustments) > invert (ctrl-i).
From the layers palette select blend mode to ‘colour’ from the drop down menu.
Reduce opacity % to the required amount (top rhs of layers palette).
Next adjust Hue and saturation if required.
Method 2
Do one of the following: Choose Enhance > Adjust lighting > Levels …
Choose a colour channel to adjust from the channel pop up menu: …
Drag the middle input slider left or right to add or subtract colour.
Click o/k when you are happy with the overall colour.
Method 3
Open the file in camera RAW.
Click on the white balance tool (third from left on the top row).
Select a mid-grey area (clouds work well).
This should remove the colour cast and bring all the other colours into line.
If it does not then keep clicking different points until you get a good result.
This will get you close to the correct white balance.
If not you can use the target adjustment tool to change the hue/saturation and lightness of the colours (5th from the left in camera RAW).
Then going to the HSL/greyscale pane on the left hand side I selected saturation and placed the tool over the area I wanted to change.
Hold in the mouse button and drag to the left/right to increase or decrease the saturation.
Method 4
. Open your jpeg image in photoshop >
. Duplicate the image so you are not working with the original >
. Select enhance > adjust colour >
. Remove colour cast > select eye dropper >
. Select areas in the scene containing greys , white or black, again clouds and rocks work well >
. select o/k when happy with the result or reset to go back to the original image.
Method 5
. Open the RAW file in photoshop RAW edit
. Move the Tint slider to the left until the colour cast has been removed i.e. -30 for an ND 8.0 3-stop light reduction.