How can I make a the lighter colors of a greyscale image transparent?
The effect you are after can be achieved:
- Duplicate the image layer containing the forrest image
- make the new layer black and white
- invert the colors (ctrl/cmd+i)
- on the black and white image: select all (ctrl or cmd + a)
copy the selected
click the original image
- create an image mask
- go into channels
- select mask channel
hide the duplicated black and white image (that you used for the mask)
this should create a mask that makes the lighter areas more transparent.
Read more on the subject here: http://carijansen.com/2004/07/25/layer-mask-from-grayscale-image/