Difference masks for Product photography
If you are doing product photography where things are not usually moving your masking job just got a hell of a lot easier: Difference masks.
Make sure nothing in the scene with your subject moves, this goes for changing lights, moving flags or gobos etc.., the scene must be static. Shoot on a stand and use a remote to trigger the camera so you don’t get any movements at all.
This technique works best of you are already shooting on white seamless backgrounds.
Now take the photo of your subject. Carefully remove the subject from the scene and take another photo.
Import the 2 photos into Photoshop and put them on different layers, order doesn’t matter.
Now for the magic. Select whatever layer is the top layer and change the blending mode to Difference and voila, whatever was changed will become black and the rest of the scene will be white or at least very bright. Hit control+shift+alt+e to create a copy on a new layer on top of all the others and hit control+u and pull the saturation down to make the mask black and white. Go to your channels palette and grab the blue channel and make a copy of it. Now hit control+m to bring up curves and drag the white/black input sliders to wards the middle to make the mask all black and white and clean up any gray areas. Control+click the channel to load it as a selection and go the the layers palette and select your original image, click add layer mask and there’s your masked out image.
