A version of this tutorial first appeared in the August 2004 issue of SBS Digital Design
Before adding light streams to any image, you first need to ask: Where is the light source for the streams? What aperture will the light be streaming through? What is in the path of the streams (furniture, tree branches, etc.)? Once youíve made these decisions, we can begin.
1 Make a new blank layer, select a hard, black brush, and paint over the aperture where the light will be streaming through. This might be a window, the business end of a flashlight, or a gap in the trees. For this image, the aperture is the manís head. Be as accurate as possible in your painting, itís the little nooks and crannies in the aperture that give light streams their character.
2 With the black painted aperture layer selected, open Filter > Blur > Radial Blur. Crank the blur amount up to 100, set the method to Zoom, and the quality to Draft. Move the blur center over your light source, and click OK. Since thereís no preview, this can be a bit tricky. Donít be afraid to undo and reposition. If your light source is out of the image frame, enlarge your canvas so you can reach it. I chose a spot on the manís forehead for my source. Once you have the blur originating precisely from your light source, run it several more times. For this image, I ran it 10 times. Then change the quality setting to Best, and run it one last time.
3 Use the Edit > Transform options to scale and shape the light streams. If you move the center point of the transformation outline to the center of your aperture, you wonít need to reposition the streams after transformation. Zoom out and drag the handles beyond the canvas if necessary.
4 The light streams will be used as a layer mask, so place them over a white filled layer and merge. If there are objects in your image that will block the streams you can make additional masks. Here I made a mask layer just of the man and combined the two by setting the blending mode to Lighten. Select the entire canvas (Cmd/Ctrl + A) and copy all the mask layers to the clipboard (Shift + Cmd/Ctrl + C).
5 Select the background layer and Opt/Alt + Click its eye icon to make it the only visible layer. Make a curves adjustment layer, but click OK and close the curves dialog without making any changes. Opt/Alt + Click the layer mask icon on the curves adjustment layer to bring it into the editing window. Press Cmd/Ctrl + V to paste the clipboard contents into the editing window and Opt/Alt + Click the layer mask icon again to hide the layer mask.
6 The light streams are not visible yet, and making them visible is a two-part process. Double-click the curves adjustment layer to open the curves dialog and adjust it to darken the non-stream portions of the image and click OK.
7 Duplicate the curves adjustment layer, click on the layer mask icon, and press Cmd/Ctrl + I to invert the layer mask. Double-click the adjustment layer and adjust the settings to lighten the actual streams and click OK.
The original image hasnít been altered, so you can continue to edit it and add additional adjustment layers. Watch out for visual cues that contradict your new lighting. In my final image, I darkened the bottom edge to hide a contradictory shadow and lightened some of the skin areas on the right side to match the left.