but since you are not actually providing any tangibile product, I would say a digital copy is not taxable
In my opinion, the USB with digital images is a product (similar to prints) which would be subject to sales tax. Your sitting fee (including studio time and travel) is a service which you provide, and in many states is not subject to sales tax. Pricing for the prints should include post processing.
I live in the state of SC and I am filling out a DBA (Doing Business As) form. Its asking me this question: "Will this location have any retail sales, transient rentals or any out of state purchases subject to South Carolina Use Tax?" I am starting a photography business, I will not be selling prints but am selling digital copies on usb to my clients. So would I answer yes or no?