Using someone else's work as a reference for your art is considered making a derivative work, and is only allowed under copyright law with permission, even if you are working in a different medium or making changes to it.
I do some figure drawing myself on occasion (poorly) and I understand the need to practice, so I allow artists working in traditional media (drawing, painting, or sculpture; NOT photography, digital art, collage, mixed media, or video) to use my photographs as a reference for their own work, with some limitations:
You may not sell the resulting piece or license it (free or otherwise) to be used for editorial or commercial purposes.
Whether exhibited online or offline, the work must be captioned "After Richard Tallent, [year]", where [year] is the year I created the original piece (the first 4 digits of the reference number). This convention has been used by artists for centuries.
Linking or tagging me is appreciated but not required. Please do NOT tag model(s) without their direct permission.
You must anonymize the model's identifying features (such as unique tattoos). My model release, which covers the models' release of their rights of publicity or privacy, does not extend to other artists.
I don't allow my work to be used as reference for any art that promotes violence, hatred, bigotry, animal cruelty, homophobia, sexism, classism, or religious extremism, nor in any work that is sexually explicit or sexually charged.
I love seeing what artists create! Please send me a photo of it via email. :)