I may be wrong, but as far as other arts are concerned; often if you are donating photographs to the event (digital or physical) you can have a sort of "bill of receipt" written up with the fair market value of what you give them. For instance if you are giving them a digital copy of a photo with rights to be used in a print campaign, then you can mark on your tax return a donation in the amount of what you would typically get paid for that photo. Digital makes it a bit of a fine line, but that's how it was explained to me by a tax professional.
Edit: That explanation is a bit confusing, but think of it this way. If you were to purchase the photograph from yourself (or someone else, if that's easier to understand), then it would have value greater then that of the materials. If you donated a photo your purchased, your donation would be the value of the photograph as a piece of art, not the value of the paper and ink it was printed with. You can deduct a fair market value for the product, but not for the service of making the product.