ZBrushCentral

crediting a photographer for reference material?

I recently did a sculpt to practice sculpting women, based on a photo I found online. I’m curious about crediting the photographer for use in my portfolio.

My sculpt is a 3D interpretation of a 2D image. The pose and clothes are the same, but I had to make up what you couldn’t see in the photo, since it’s from one angle. So I guess the real question is, where is the line between reference and using the photographer’s work?