On this video tutorial Aaron Nace from Phlearn demonstrates how to change a model’s proportions in Photoshop.
As Nace mentions in the video, altering a model’s body proportions is a very controversial topic these days. In some countries there are even laws which either prohibit or in most cases mandate advertisers to publish a notice each time a model was altered significantly in an image.
Moving from the cultural and legal aspects to the technical side – Nace demonstrates how to do a transformation that will not push the limits too far (although the final results is of course up to you). Nace start with two things which might sound a bit strange, but actually work pretty well – the first is making the legs a bit longer and the second is making the neck a little bit longer – both things tend to make people look slimmer without changing too much.
Nace shows a few different techniques for changing a model’s body using puppet warp. You start by creating anchor point for place which you do not want to change. This is a very simple process and it allows you to do pretty realistic changes (or very unrealistic if you take it too far). The second tool Nace demonstrates is the liquify filter (nace recommends this as a second option after the puppet warp).
Both tools have uses which are far beyond changing models – you can change objects using the exact same method and go much further and still look realistic (or not, but in the case of most objects there is far less controversy over changes you make),