After making a few models of girls, I felt like doing something slightly different. I challenged myself to make a realistic portrait, and chose to do an old man. Although some people asked me if it was an attempt at creating the portrait of an existing person, it was not. Nonetheless, of course I used lots and lots of references throughout the creation process.
I might be telling you something you've heard a thousand times before, but it is very important to get as much reference material together as possible before you begin. Also, try to get close up references for each part, even if it comes from different people and other ages than the one you are trying to achieve. If you want to achieve a realistic result, it's really useful to know how things are done in real life. Most importantly of all, you have to take the time to observe and understand how everything works (muscles, fat, wrinkles, bones, etc.). Take some time to study the details and don't forget that 3D software is just a tool, and that to make a realistic human character requires a sold knowledge of anatomy.
You'll find tons of references on search engines and on websites like 3dsk. Here are a few thumbnails of some references I used for this project (Fig.01).
Before we start, I would like to tell you that it took me several months to achieve this result, because I was learning as I went and it was all during my spare time. So, instead of explaining all the phases of the original creation process (which probably wouldn't be interesting), I'll detail the workflow I've put in place and that I will use from now on.
As a common workflow, I started with the base mesh (Fig.02) and UVs (Fig.03) in 3ds Max, then imported it into Mudbox for the sculpting process.