This is the original image that we are going to make in to a 3D image.
The layer needs to be duplicated first so as we have two identical images layered on top of each other but on separate layers. We select the 'Background Copy' layer.
Then we need to change the levels by going in to 'Image', 'Adjustments' and 'Levels'
We change the channel to 'Red'
And the right 'Output Level' to 0
This is the top layer which has had the colour altered on it.
We then need to change the Levels on the other layer of the image.
We go on 'Image', 'Adjustments' and 'Levels' again to alter it.
This time we change the green level.
And set the right 'Output Level' to 0
These are the colours of the layers now that the Levels have been altered.
Changing the Layer setting to Screen makes the image look relatively normal again.
This is the image when the Screen Layer effect is applied to both of the layers.
Then we need to move the images apart slightly and this can be done by selecting the 'Move' tool and moving the top layer image down and to the right slightly.
This is the final 3D image that is produced and you can see that the two colours of the images are slightly apart from each other.