On this video tutorial Aaron Nace from Phlearn demonstrates how to swap heads between images in Photoshop.
Swapping heads in images might sound strange (and maybe a bit perverted) but it is actually a very useful technique for situations where you have a several group photos and one or more people do not look good in some of them but look O.K. in others.
First we need the images (at least two although you might do that with more if you need to swap more people). We start with the move tool and bring one image on top of another and create a new layer. We make a selection around the face and make a layer out of it and make sure it is partially transparent. We need to make a match between the two heads and try and fix all the small places which still does not match using clone stamp. Nace suggest that we try and replace as little as possible to make the image look as natural as possible.
Nace makes this look simple and in some cases it really is – however especially when people are close to each other – this can get pretty tricky. As long as the images are similar this might work – this is another good reason why you should always take a quick series of shots when you make a group picture.